With the flop bet not thinning the field and not generating any raises I would have concluded that I was likely good and that there were no big draws out - I was probably up against a couple of weak draws and another 9 that didn't know where they stood. Unlikely the 3 helped anyone unless the spade gave them a draw as well as a piece. The 2 checks just serve to reinforce my conclusion so that tells me I should bet. I check the river and call the button's reasonable bet (but would have folded to a lead by either blind) - I assume you paid off a 9s based flush. Tough hand.