Like others have said, HTBT... If the kid was acting like a jerk, this could be the last straw. For me, I guess it depends on what, if anything, the player might have done earlier in the game... I'm not sure just slapping the ball would warrant a T, but it might if there was more to it.
I T'ed a kid this year because he threw the ball at me... sort of. It was mostly an ABS.
I had called an off-ball foul (on a different player) and was going toward the table to report and the ball bounces off my shoulder -- hard bounce-pass, at me, apparently. I continued with my report and then turned around to warn the kid, only to find him arguing with my partner about what he did.
I wasn't going to, really, I was just going to warn him. Never mind. Whack. He'd had a bad attitude and was whiny about several calls already. Enough.
Coach: What did he do?
Me: He's had a disrespectful and unsporting attitude toward both me AND my partner all game... and he threw the ball and it hit me.
Coach: Really?? Sorry.
The kid sat for the next quarter and a half.