I'm so sorry. D: I hope you find him.
I've had my betta for over six months, and he's never tried to jump out of his tank. I didn't even know he would be able to. I've always filled his bowl so it's just two inches below the rim. Right now his new tank is about three inches below.
Maybe he's still in his tank? Try taking everything apart, including every part of your filter. Hopefully you can find him, and he's alright. D: Good luck.