[Massad]

I think it's an easy 3-bet on the river. Conceivably he could have raised on the button with 43 trying to steal the pot but it's much more likely than he rivered Aces up or even just a pair of Aces. Remember you are playing 5-handed here, there was no reason for him to give you credit for a good hand neither. Even if he caps I would still say your set is good more than 50% of the times.