just from my perspective maybe had you just flatted and got to the flop without committing all chips preflop, your villian may have felt that he was beat by the turn with the overcards on the board. he may have folded to some forceful betting. but it's hard to say when u r heads up like that because it takes soooo little to win a hand (by little i mean 33 is a made hand, where A8 is behind and needs to pair). sometimes those 3's are gonna feel like aces you know? he obviously thought u didn't have a pocket pair to call with 33 there and thought he was favorable to win.
idk with that kind of cash at stake... i wouldn't be putting all my money in preflop with Ahi hoping to win a race for the extra 15k... i'd be playing to see flops, and outplay my opponent post flop and let him make a mistake and capitalize on that. but even in that case had you played to the river with villian calling you down with 33... there's no way you're gonna put him on pocket 3s HU when the 3 fell on the river, and those trip 8s were gonna cost you no matter what.
with that said, congratulations on your 2nd place finish, and a nice cash at that! so you got unlucky on the river... it happens, shrug it off and keep playing solid poker. to survive a large field, like you did in that tourny, is a victory in itself, and you must have been playing solid 99% of the time!