Sounds like you just ran into some bad luck. I would have done the same thing if I were you based on what I would have done as the SB. I would have made the same play as chip leader in SB thinking my 3s are good enough to push you since odds are you dont have much in terms of cards. You were about an 77% favorite PF, I guess the guy caught his set of 3s. Good stand, bad luck.