Use the type of thinking, what are the possibilities he has the queen. If it's greater then 50% (or whatever odds you need) that he doesn't call.

It is VERY likely he has the queen. How the hand is played. He probably had Q no kicker. The flush scares him, then he hits quads on the river.

Either that, or he slowplayed the flush, and was upset that you beat him on the river and wants to bluff you off it.

Considering this is 25nl I'm 90% sure he has the Queen