"He's absolutely fine...He's a very lucky man," Mr Thomas said.
Mr Stilwell was on a night out with fellow travellers when he got separated from them and went home to the Volt apartment complex, on the corner of Queen St and Mayoral Dr in the central city.
He woke a neighbour and asked her if he could lower himself down from her top 15th-floor balcony to his own, directly underneath.
Geraldine Bautista, 28, said Mr Stilwell slipped from her grasp and plummeted "like a paper falling".
"He never said anything ... I grabbed his hand and then at that time ... he fell down. I thought I was dreaming. It happened so fast. It happened within seconds. I couldn't even scream for help. He was like a paper falling from here."
Mr Stilwell knocked on Ms Bautista's window about 2am. He was "a little bit tipsy".
"I wasn't scared of him - he just requested 'Can you please let me jump off from the balcony? I will not bother you just let me use your balcony ...'
"I never thought he would really do that. In my mind I thought 'Okay, I'll just let you see that it's really impossible [to gain access to his apartment]. I didn't think he'd jump, because it's really scary."
He walked quickly through the flat and onto the tiled balcony which is less than a metre wide. Before she could react he had one leg over the railing.
"I asked him 'Are you all right? It's unsafe to jump over the rail'."
Mr Stilwell plummeted about 13 storeys before landing on a roof of an adjacent building - something one medical expert believes could have saved his life.
Ms Bautista raced downstairs while others in the building called emergency services.
A flatmate slept through the drama but spent the rest of the night comforting her.
Mr Thomas, who said his friend had a "fair bit to drink", was only 10 to 15 minutes behind Mr Stilwell. When he and a third flatmate got to their front door, they were met by police searching for identification for the injured man.
He said the incident was not typical behaviour for his friend - "he's normally the sensible one out of all of us."
St John medical director Dr Tony Smith said surviving falls from such heights was "extraordinary", but a person's chances increased greatly if something broke their fall.
"We've seen patients in Auckland who have had their falls broken by awnings over windows, umbrellas, those sorts of things."
But the roof the man fell on to would not have prevented serious injury.
"From that sort of height you can have injuries to everything and anything. Survival from falls of that height are extraordinarily unusual."
And there was no evidence to support the belief that alcohol relaxed the body, making it less likely that a person who had been drinking would be injured in a serious fall.
"It's like being in car crash. If you're going to hit something at speed, relaxed or not is not going to make too much difference."
Mr Stilwell is from Brighton and works at Auckland Transport. Mr Thomas was unsure if Mr Stilwell's parents' were flying to Auckland to be with their son.
• July 2010: A 15-year-old falls 50m from a Manukau apartment block onto the roof of the car park building below.
• July 2011: A window cleaner falls six storeys from a building in Wellington landing on a car - and dislocates a toe.
• December 2011: Acrobat plunges six storeys from the Metro Centre in Auckland.
