McGowan collected the sponsors' man of the match award for his contribution to St Mirren's 3-2 victory over Hearts and he savoured Hampden celebrations he thought he might never see.
The 25-year-old, who had played in the Champions League and Europa League for Celtic, joined St Mirren on a permanent basis in the summer of 2011 after playing for Danny Lennon on loan the previous season, and the creative midfielder has developed into one of the most effective players in Scotland.
McGowan said: "I bit the bullet and left Celtic, which was hard. If I'm honest, I never dreamed I would win a trophy with St Mirren but I will cherish it for the rest of my life and I'll be thankful for the gaffer taking a chance on me. It has worked out great.
"It's incredible. I could sit here and talk about it all day, it's a great feeling."