The 33-year-old had on January 5 climbed to the top of a 20m-high crag (about the height of a five-storey building) at Hospital Flat, near Wanaka and was preparing to abseil down.
He hooked on to the wrong line, and fell to the ground. By all accounts, he should have died. He still marvels at his extraordinary survival.
He broke his back and both legs in the fall, and there had been a time when he thought he would be confined to a wheelchair for the rest of his life.
Yesterday, Mr Stewart recalled his close call with death.
''I hit and ... one of my climbing partners said I didn't make any sound for about 20-30 seconds. He thought I was dead.
''And then I started moaning because my back hurt.''
One of his fellow climbers was a doctor who helped stabilise him until emergency services arrived about an hour later. He was conscious throughout.
''It was pretty excruciating in my back and right foot.''
He was flown by helicopter to Dunedin Hospital where he underwent surgery twice,
including the insertion of a plate with 12 screws to repair his shattered right heel.
For the first few days, he worried about getting back to work as a structural engineer at the Five Mile Retail Centre development in Queenstown.
''But a day later I was just thinking about surviving.''
It was not until three days after the accident that he learnt the spine fracture was stable and he would eventually walk again.
''I actually felt really blessed, because I could have easily died. I could have had really bad head trauma, a complex back fracture, and if I had landed half a metre to the left or right, I would have landed on a boulder instead of a grassy slope, and that would have been the end of it.
''I still can't believe that I survived that fall.''
After nearly a month, he was allowed to leave the hospital, and stayed in Dunedin for treatment. He hopes to return to Queenstown this week, where he will re-learn how to walk.
Mr Stewart has been mountaineering near his home in Lake Tahoe, in the United States, for the past eight years, and began rock climbing last year. The incident has made him reassess his priorities in life.
''Queenstown and Tahoe have pretty similar lifestyles. I think it's a selfish lifestyle because it's filling us with what we want. It's a need for adventure.
''My parents came out to New Zealand to look after me. To me, that's such a selfless act.
''It really makes me think about keeping contact with people more, and maybe thinking that I should in the next few years, think about settling down, getting married and having a few kids.''
He believes he will eventually return to mountaineering.
''Mentally, I'm ready to do it.''
