Using Basic Poker Tells

This weekend at the poker tables in Atlantic City, I played in a sit-and-go that paid the top 2 players. There were 3 of us left. I looked down and found Ace-nine suited UTG, and raised the pot to two times the big blind, which had been enough to steal the blinds before. The small blind then pushed all in. What to do, what to do. Ace-nine is a strong hand when there's only 3 people left, but was this the hand I wanted to go all-in with?

Then I noticed something, Mr. Small Blind was "Acting Uninterested in a Hand While Still in It," which is a basic poker tell that says "I've got a great hand." I did a few chip tricks to see what his reaction was when I went to grab some of my chips, and decided to muck my hand. Was it a good laydown? I think so, especially since I ended up splitting the prize pool 50/50 in the end. But what would you have done with that Ace-Nine?

Edited to add: Also, it should be noted that Mr. Small Blind and I were about evenly stacked (I was a little ahead) while the 3rd player in the big blind was severly short-stacked.