What makes a straight here, 69, J9, 64... those hands in diamonds are conceivable but hardly likely (especially with a BU open m/r).

So, I kinda doubt he put you on the straight here. More likely he was just semi-bluffing all the way with 2 diamonds. Plus, your river bet was weak, so he probably calls here with TPGK+.

I don't hate your turn call since at least you have 3nd pair + flush outs... it's pretty thin though, especially when your draw is not anywhere near the nuts... and clearly vs. this guy your implied odds weren't there either (if he really did fold TP when the flush DIDN'T hit).

Don't do this against 50NL unknowns - only people you think are paying attention, or have been especially weak.