Hibs exacted sweet revenge for their 5-1 thrashing in last year's final with a scrappy 1-0 victory in the fourth round tie at Easter Road.
McGlynn said: "We're all absolutely gutted. We're the holders of the cup and you don't want to lose it.
"We put a lot into the game and so often we've said this this season, we came away with nothing.
"We started the game very well and had a couple of really good opportunities.
"We were in control of the situation at half-time. In the second half, the longer it went it looked like it had 0-0 written all over it.
"We certainly never looked like losing a goal but Hibs got the one break in the game. It's a massive, massive deflection, Jamie MacDonald can't really do anything about it at all."