A woman who believes missing Auckland mother Carmen Thomas cried out for help at a supermarket carpark days before she went missing is plagued by guilt that she didn't speak to her.

Ms Thomas, 32, has not been seen alive since July 1, and police say her disappearance is looking sinister.

Nataly Ireland, also 32 and a South African native, has been haunted by an encounter she believes the pair had towards the end of June.

The mother of three cannot remember the exact day it occurred but thinks it was between June 25 and 27, when she pulled into the Greenlane Countdown in Great South Rd.

She left her three children in the car while she went in for a few groceries, and believes Ms Thomas walked towards her across the carpark, with two other women.

"I am very sure I saw her and she wanted to ask me something serious, but then changed her mind," Mrs Ireland told the Herald. "I feel guilty for not asking how I could help her and that is how I emotionally feel that I owe her."

The Greenlane resident has reported the sighting to police who say they have security camera images of Ms Thomas on a night out with two girlfriends in Newmarket on June 25.

"Yes, she's been spotted with two friends on the 25th, that does follow," said Detective Inspector Mark Benefield, who is heading a police team of 30.

"We have footage from the 25th and the 27th and that was life as normal as far as we can tell ... We're quite comfortable with the 25th and the 27th."

He said all reported sightings were taken on face value until proven otherwise, but sometimes people "second-guess what they think they've seen and it keeps playing on their minds".

The mental image of the Ms Thomas-lookalike is tormenting Mrs Ireland.

"She looked at me as if she wanted to say something but then looked at the kids in the car and changed her mind," she said. "Her face just looked troubled ... She looked like she was concentrating or focusing on something ... It's one of those facial expressions that's so hard to describe."

Despite never having met Ms Thomas, Mrs Ireland said she was passionate about helping find her.

"It's because I didn't ask her, 'How can I help you?' I look at my daughters and think what if it was them ... She wanted to say something."

Ms Thomas' mother Teresa Scott - who travelled to New Zealand from South Africa on July 23- has since twice seen her 5-year-old grandson Jack, who is being cared for by his father.

On a social networking page set up for Ms Thomas, numerous friends beg for information and say she would not have left Jack by choice.

"Carmen idolises her son Jack and there is no way she would just leave him. Please, please help find her," the page reads.

Mr Benefield said Ms Scott would return to South Africa at the end of the week unless "something popped out of the woodwork that would keep it going".

Meanwhile, the owner of a private men's club where Ms Thomas worked has offered to meet Ms Scott.

"I've told police I'm more than happy to meet her," he told the Herald.

"To go out and have a coffee or chat and just basically put her mind at ease that it was not a seedy thing she was doing ... She was working in a legalised industry in a legalised place with people who run a business, as a business."

A couple of clients had asked if it was the same woman and were distraught to hear the answer, he said.

As a parent, the agency owner said, he would be "climbing the walls" if he couldn't find one of his children.

Anyone with information on Ms Thomas' disappearance should contact police on 0800 KEPPEL (0800 537 735), via email address whereiscarmen@police.govt.nz or call Crime Stoppers anonymously on 0800 555 111.
June 25: Security cameras show Ms Thomas on night out in Newmarket with two women friends.
June 26: Nissan Pulsar (registration ATS209) parked in Sylvan St East for several hours, from just after midnight.
June 27: Security cameras show Ms Thomas at Greenlane Countdown.
July 1: Last seen in Auckland.
July 3: Last contact: text message to owner of Pakuranga gentlemen's club where she worked.
July 5: Ms Thomas' abandoned car found in Hamilton with temporary tyre on left rear.
July 13: Ms Thomas reported missing after failing to pick up son.