Then followed an email from another of John's daughters, who had lost touch with him but knew he had married a woman called Lyn and had moved to Perth about 30 years ago. That was an ironic twist - 51-year-old Kim has lived in Perth for the past 20 years.
So she got to work and found a phone listing for J & L Clark, and made the call. "I said to him: 'John, did you know a woman called Shirley?' And he said, yes.
"Then I said to him, 'I'm her daughter', and he just said, 'Oh my God' ... I said to him, 'Can I ask you a question: are you my father?' He didn't even hesitate. He just said yes."
The pair met within days and did the DNA test and then settled in for an agonising two-week wait.
New Zealand is dotted with the children of overseas soldiers and sailors from World War II and subsequent wars.
Dr Gabrielle Fortune, a research fellow at the University of Auckland's History Department who also works in the military section of Auckland Museum, says some men returned from war to find their wives with babies that couldn't possibly have been theirs.
Often, they opted to stay with their wife and get on with life, reasoning that neither partner had behaved perfectly - but at least they had both survived the war.
The child was often unaware their dad wasn't their biological father; one man found out in his 60s, after his dad had died, that he was not his natural son.
"It's a horrific thing to suddenly be told," Fortune says. "It can be good if it works out but it can be devastating if it doesn't."
Fortune has started taking the names of people who come to her with queries about how to find a parent on the off-chance it could one day help someone connect the dots. Her register of estranged fathers and children is far from complete.
"It has some names on it but it is tiny," she says. "The short answer is, you need a lot of information to find someone."
Two weeks ago wasn't the first time Kim and John met - he held her once when she was an infant, an experience that left him "flabbergasted".
John had met Kim's mother when he was a steward in the British Merchant Navy. He sailed between England and New Zealand on the New Zealand Shipping Company vessel Ruahine, bringing people out, taking frozen lamb back and enjoying shore leave in between.
Kim's mother captured his heart and he decided to move out permanently, and they got engaged in 1960. But a few days before his one-way flight to New Zealand, Kim's mother ended the relationship. She was pregnant and initially said the child was John's before recanting.
John was just 19 or 20, and says now he simply didn't have the wisdom to insist on being part of the child's life. "She just didn't want me to help or do anything," John says. "At that age you think, 'Oh well, that's it.' You just haven't got the wisdom."
He used to wonder how the child was but never got in touch, not wanting to put a spanner in the works. He got on with life, married another Kiwi woman and soon after had another daughter, Tracey - the daughter who emailed Kim.
Meanwhile, a young Kim was brought up by her mother and new partner. Then, when Kim was about 10 her mother married another man - the one whom she says would only ever call her "dummy".
When the couple went out, the young Kim would sneak into their wardrobe and go through a photo album her mother kept hidden there. "It was full of men and women and parties they used to go to," she says.
"I used to get it out when they'd go out and look through it, and I used to think, 'Which one of them is my father?'
"It's funny because Johnny Clark ... he was the one that always used to jump out at me. I felt like I could see a resemblance in him."
When she was 22, her mother finally told her who her father was - but it wasn't the man she thought she looked like. Instead, her mother nominated Billy MacDonald, a Scotsman in the Merchant Navy with whom she'd had another fling, but who had returned to Scotland. Kim didn't believe her.
It wasn't until Kim was 29 and had her own daughter, Brooke, that she decided to track down her father.
"Probably when I became a mother myself I really wanted to know for DNA reasons ... genetically what I was passing on to my daughter," she says. "It sort of came back to really haunt me then."
She always focused more on finding Johnny Clark than Billy MacDonald - there was the resemblance, and the fact that trying to find a man of that name in Scotland would be "like looking for a needle in a haystack".
She went through phone books, contacted the Salvation Army, and went through the New Zealand Shipping Company's records and ship logs. Nothing worked but the elusive truth always niggled away.
Finally she placed that ad in the newspaper while back in New Zealand on holiday. The outcome, it seemed, was the answer to her dreams.
Michael Gaeng knows the uncertainty Kim has been through. Fourteen years ago he finally tracked down his father after years of trying.
Sadly, it was too late for the pair to meet. The former United States Marine had died only five years earlier.
Michael had been looking for Kenneth Geange - a spelling mistake which meant his father died never knowing he had fathered triplet sons after a brief liaison with Ina Hohaia while in New Zealand.
Ina, a teenager with schizophrenia, wasn't a good mother. "She used to do a lot of cruel things to us. I got extremely bitter as I was growing up," Michael says.
Often the boys - Michael, John and Graham - went hungry. Neighbours who sometimes fed them called social welfare, and the malnourished trio were put into care on their 5th birthday.
Michael remembers the day, which started with their mother telling them there was a railway bridge on the way to school and they should "jump over the bridge and don't come home".
"Well, she got her wish because we didn't come home."
Instead, they were placed in six or seven foster homes during the next four years before finally finding a good home with Tom and Kahu Whiteley at Te Teko, in Bay of Plenty.
"They were marvellous. Wonderful, wonderful people," Michael says.
Michael and John stayed with the Whiteleys until they were 22; sadly, Graham died of cancer aged 19.
Ina died young, but Michael tracked her down before she did and made his peace with her. She was in a mental institution and it was during a visit that he spotted a letter with what he thought was the name "Kenneth Geange" on it. When pressed, she said he was the triplets' father.
That started his long and expensive search for his dad.
Michael received knock-back after knock-back but he kept trying and, finally, a small change of tack got a result. He sent a query to the National Records Centre, where US military records were kept, asking about Kenneth Geange and Kenneth Gaeng. The request paid off and in 1999, Michael got the letter he had been waiting for, providing his father's name, his wife's name, Rosemary, and where they lived.
Michael got on the phone immediately, and by the next day he knew his father was dead - but that he had a whole new extended family. That he had the right man was in no doubt; he and his son Justin both bear an "unbelievable" resemblance to Michael's father.
A year later, Michael and Glennis, with his brother John, went over to meet their new "American family" - six half-brothers, two half-sisters and their children.
When they landed there was a big banner on the wall of the St Louis airport that read "Welcome home, brothers". They stayed in their father's house, with Michael sleeping in his bed.
"David, another one of my brothers, said: 'Mike, for all the work and time that you have done to trace us, you are going to sleep in my Dad's bed.' It put a shiver right up my spine. I just don't know how to describe it."
That was 13 years ago and the family remains in close contact.
Michael knows his experience has been a good one with a happy outcome, but he says anyone searching for their parent should keep on trying despite the inevitable knockbacks.
"Keep plugging and don't give up," he says.
Be persistent - that advice is echoed by Dr Angela Wanhalla of the University of Otago, who is researching the social impacts of the relationships between American servicemen and indigenous women in the Pacific. "You have to be prepared to be creative in your searches - putting in notices in newspapers, things like that are a really good thing to do," Wanhalla says.
"Don't give up, be persistent, because at some point you may get that key piece of information that you need that's going to move you on to the next phase of the research.
"Most people just hope for confirmation of their father's name, that their father actually existed and was in New Zealand and this was the person that was their father.
"Sometimes they hope for making an emotional connection with family. Possibly they've grown up where they haven't had that emotional connection with their own family, and so they're hoping to repair past traumas and to build a new family life."
Wanhalla's project started in 2010 and is focused on the American servicemen in WWII, but she says there are parallels for the children of servicemen anywhere and, indeed, any illegitimate children. "The Merchant Navy, because they're always moving around different ports, you do tend to build relationships in all these different places you go to," she says.
"Like the American servicemen, those relationships can be of a whole range of types. Sometimes they can be very brief encounters, short romances, a one-night stand sometimes, and others can be much longer term."
It is easy to forget the shame that was once attached to having an illegitimate child, for the mother and the child. Such women also had to cope with rejection, and their children often inherited the shadow of that, says Wanhalla.
"They grow up with the burden of that, particularly if your mother doesn't want to talk about it or if your mother has kept it secret from you, or built a new relationship after the war and married - it's even more important for those women that you keep it a secret," she says.
Michael's story is one of those with happy outcomes, but Wanhalla warns anyone looking for their parent to be prepared. "They may be just too shocked to respond, or have never thought their father was that type of person," she says. "I think we all grow up with ideals about our dads, and sometimes the notion that they could have once been young and carefree and may have left children behind during wartime could have been a real shock for some people."
It is Friday afternoon, and Kim has been on tenterhooks all day. She feels incredibly stressed, she admits.
Finally, late on Friday afternoon, the phone rings. It is the call from the forensics lab that she has been waiting for - but the news is not what she hoped and so confidently expected. The DNA test rules out John as her father.
Kim is in tears. She is, quite simply, "devastated", she says.
Now, like so many other New Zealand children of overseas soldiers and sailors, she has a tough decision to make. Does she continue to live without knowing who her dad is, without knowing an entire side of her family - or does she, again, go looking for her father? No doubt, there are a lot of Billy MacDonalds in Scotland - but if anyone has any information on him, she'd love to hear from them ...
If you know MacDonald, email news@hos.co.nz
