On Saturday, the Aberdeen-born hooker's rapid rise continued as he made his Scotland debut, playing his part in a comeback win over Fiji.
Stephen said it was the fulfilment of a long-held ambition.
"I was saying to the boys in the changing room that I remember being here in 2024 sitting across the other side of the pitch with my dad and my brothers, watching Scotland play South Africa and I thought: 'That's all I want to ever do'.
"From being at the junior academy a year ago then coming through to Glasgow, never on my radar did I see this opportunity, so it has been amazing."
His path to a first cap was unconventional. After the U18 Six Nations, Stephen was not offered a contract by Scottish Rugby and instead moved to New Zealand to play for the University of Waikato.
"After under-18s, I don't know if it was a mixed communication, but I didn't really get anything offered so I thought I didn't really have anything to be waiting around for, and I wanted a different experience, so that's why I went out to New Zealand.
"I think I was slightly egged on by my mum and dad, because they just thought, 'what a time to have that experience in your life'.
"I had my 18th birthday out there, which is pretty rogue to do, I suppose, but it was a good experience."
He had planned to remain there until a call from Scotland U20 coach Kenny Murray changed everything.
"I was originally going to stay out there. I didn't have a time to come back so I was just enjoying playing out there and then I got a call from Kenny to come back.
"After that, I was a player of national interest.”
Glasgow signed Stephen and his performances earned him a place in Gregor Townsend's Nations Championship squad.
Now he wants to build on his first cap.
"There's a lot of good hookers in Scotland, so I think I'll have to do a good job to stay in here, but I think that's just through playing well for Glasgow.
"Hopefully I'll get another crack at it, but I loved it today. So I just want to keep doing it."
Stephen also knows where he can improve.
"I'd say probably around my carry. That's probably something I really want to focus on. You've got so many great ball carriers like Rory Darge and Matt Fagerson, so they're such good people to learn from.
"If I can make that really strong then that'd be great. But I'd just say set-piece as well. If I can nail.”
Having his family there made the occasion even more memorable.
"I probably had about nine of my family in the changing room, so it was a bit cramped, and then more friends and family as well in the stands - it was great that I had their support.
"I could see my mum and dad while I was going up to get my cap. To have them there, I feel like everything they've done for me is amazing. It was very special."