Is a river check-behind a leak here? Cuz I would lean more toward that...one of the most likely draws got there on the turn when you improved as well...he smooth calls a 2/3 flop bet and turn overbet...and he's not reraising the river with QJ/KJ/JT.

The oddest thing here is that I would expect him to lead the river out of position if he knew his hand was best. Given that he didn't, calling his river minraise is a given.