OTR is tough. You can't really put anyone on a hand because of all the checking.
This is a great example of why aggression is such a key element in poker, and hold'em in particular. Betting clarifies your opponents' hands.
In this case, the 9 hit the river, and a 9 would probably be within a reasonable villain's calling range after the turn, so you'd have a tough time calling whether you had bet the turn or not. But that's a fairly rare outcome, not such a great example. Instead of focusing on this one result, think of where you'd be if any one of the other 43 cards had hit.
Unless you spike a queen, you're lost if someone bets into you because you didn't clarify their hands at any point after the flop. Now you're stuck reacting with a bluff-catcher in an awkward spot. You're up against 3 opponents who could have anything they would've played preflop for one raise—small pocket pairs, connectors that hit an ugly gutshot, whatever.
Compare that to betting the turn: Maybe everyone folds. Winnah!
Or maybe Asian Dude calls with a 9, and you make money every time he doesn't hit that 9 on the river. You may even be able to squeeze in a thin value bet on the end if you know your man. Or maybe he check-raises you, and you can snap-fold QQ with a smile on your face.
Aggression, dude. Used judiciously, it gives you a lot of information and a lot more chances to win.