The Double Dribble

[Adam]

Are we talking HS rules, NCAA rules, or FIBA rules?

Seriously.
A couple of things. First, in pickup ball you have to go with agreed upon rules. My advice here is just to go with it, and use it against him sometime.
Secondly, by throwing it off of your body, he is ending player control (as long as he loses possession) and may retrieve the ball with a new dribble.
Thirdly, I'm assuming you were essentially standing over him with your arms up, and weren't able to hit the ball with your hands. Don't guard him so closely. Back off a half-step and allow yourself reaction time to defend against this.
Fourth, in one-on-one ball, a lot of guys make allowances for the fact you can't pass once you lose your dribble.