Heavenly Hold'em - Commerce Casino (Did I blow it?)

[JBH]

Me:
I have played HE for about 2 months. Not a lot of experience, but haven't lost any money. Pretty much a break-even player that has a lot of leaks to plug before I start to realize long-term +EV. I was in LA on business and went in early because I wanted to play a real B&M tournament for the experience.

The Game:
Heavenly Hold'em NL tournament ($100 + 20) at the Commerce Casino. 400+ players with over 600 rebuys. A total prize of $102,900.

The Scenario:
I was very happy with my play in my first real tourney. I made it to the eighth level and finished the tourney in 93rd spot. I was probably slightly above average as far as chip position goes. Definitely had an uphill climb to be in contention for the money (top 27).

I was in the BB with K9o. One early limp, one late limp, SB calls and I checked. At this point in the tourney, I would have folded the K9o, but thought I'd see the FLOP.

The FLOP came AA9. Everyone checked, which I thought was weird, but I have seen people scared before with AA hits on the flop. The TURN comes, another A. I now have a full house, but scared someone is holding the last A, so I check. Everyone checks. The RIVER comes 6. Same situation, I check. Early Position goes all-in. Everyone else folds.

Now the real problem:
I am looking for a way to increase my stack to compete for the money and the all-in raiser jumps after the 6 hits the board on 5th street. I think he has a AAA66 and I have AAA99. I call. He flips over the 4th Ace.

Like I said before, I haven't played a lot of poker and was never faced with this situation before. There wasn't a lot of money in the pot, so I probably should have folded, but was determined to double my stack.

I got slowplayed and it cost me the tourney. Did I play it 100% wrong or would any of you played it different?

Thanks,
JBH