UB Hand

Here's a hand I played tonight from the 50-100 hold em game on UB. Somebody explain this one to me.

- 3-handed. Button folds, I raise from SB with A4o, BB calls. Flop 8s 6s 5h, I bet, BB calls. Turn 7h, I check (to check-raise), BB checks. River Th, I bet, BB calls and shows Kc9c. This has got to be a misread on the turn, right? Is there any other explanation? What about the river? He gives me a backdoor flush or J9 here? My stars. I've been hitting hands this week but man these games seem good to me.