For some reason I didn't raise pf, maybe scared of the big stack slow-playing.

Looks to me like he hit two pair on the turn? Or hit a set on the flop already? I couldn't call due to my stack size, the only option would be to raise all-in on the turn (or the flop).

PokerStars No-Limit Hold'em Tourney, Big Blind is t100 (3 handed) from (Format: FlopTurnRiver)

Button (t4450)
SB (t5345)
Hero (t3705)

Preflop: Hero is BB with Q, K.
Button calls t100, SB completes, Hero checks.

Flop: (t300) 5, Q, 3 (3 players)
SB checks, Hero bets t200, Button calls t200, SB raises to t600, Hero calls t400, Button folds.

Turn: (t1700) 7 (2 players)
SB bets t1600, Hero folds.

Final Pot: t3300

Results in white below:
No showdown. SB wins t3300.