A hand that bugs me

[phish]

Think this is my first hand post. I can usually think thru a hand myself, but this one bugs me to no end:

3 handed Stars 1/2 game. Villain is Piejay.

button folds. Piejay calls sb. I check with J6.

flop is 764 w/ one diamond.

he checks, I bet, he raises, I reraise, he caps.

turn is 5 of diamonds.

he bets, i raise, he calls.

river is Q of diamonds.

he bets, i fold.

I think the flop bet and reraise and call the cap is pretty standard. No big deal.

On the turn, I raise just in case he was overplaying a straight draw on the flop and has now hit his 5. Want to punish him. Didn't really like it because of the Stars 1/2 semi-regulars, Piejay is actually one of the less tricky ones.

His bet on the river bugs me. Would he bet a five here as a desperation bluff? I though it was more likely that he had a straight and didn't want to scare me off with a three bet on the turn. Or had the idiot end of the straight and thought he could bet the river since the diamond was a scare card that would prevent me from raising even if I had the 8. Or he made a flush.

I folded but the whole hand has really bugged me. (Maybe I should've called just to see how badly I butchered this hand and at least KNOW one way or the other.)

Comments, anyone?