You can't bluff by calling

The amusing thing here is that the villain and the guy in Seat 1 had been going after each other in the chat window virtually the entire tournament.

I wound up heads-up with Seat 1, and we were fairly evenly matched. He won because the same card that gave me a set gave him a flush. But that's neither here nor there.

Full Tilt Poker Game #_: $5 + $0.50 Sit & Go (_), Table 1 - 30/60 - No Limit Hold'em - 21:32:45 ET - 2007/06/03
Seat 1: (2,085)
Seat 2: hero (2,100)
Seat 4: (1,905)
Seat 5: (1,680)
Seat 6: villain (1,230)
Seat 5 posts the small blind of 30
villain posts the big blind of 60
The button is in seat #4
*** HOLE CARDS ***
Dealt to hero [5d 5h]
Seat 1 folds
hero raises to 180
Seat 4 folds
Seat 5 folds
villain calls 120
*** FLOP *** [4s Ad 6s]

Uh oh. My only consolation is that I don't think he would have called a pre-flop raise from me with a 4 or a 6. So it's whether or not he has an ace.

villain checks
hero bets 390
villain calls 390

Just called? Spade flush draw?

*** TURN *** [4s Ad 6s] [9h]
villain checks

I really, really, don't think he has an ace unless he's being far sneakier than I'd expect for a $5 SNG. Let's see if we can end what I believe is a flush draw. I'll put him all-in.

hero bets 660
villain calls 660, and is all in
hero shows [5d 5h]
villain shows [Ks Th]

Huh?

Maybe he was trying to bluff me, and that's fine, but if your opponent puts you all-in, they're done. They can't fold anymore. You either beat them with the cards in your hand or you lose.

Maybe he wasn't trying to bluff me. Maybe he thought his king high was good. If so, given that I raised pre-flop, bet the flop, and then put him all-in on the turn, that's just stupid.

*** RIVER *** [4s Ad 6s 9h] [2c]
hero shows a pair of Fives
villain shows Ace King high
hero wins the pot (2,490) with a pair of Fives
villain is sitting out
villain stands up
*** SUMMARY ***
Total pot 2,490 | Rake 0
Board: [4s Ad 6s 9h 2c]
Seat 1: didn't bet (folded)
Seat 2: hero showed [5d 5h] and won (2,490) with a pair of Fives
Seat 4: (button) didn't bet (folded)
Seat 5: (small blind) folded before the Flop
Seat 6: villain (big blind) showed [Ks Th] and lost with Ace King high