How would you have handled this situation?

[Adam]

so much is wrong with what he did.

1. I never stick around, but you won't see me in the locker room while my partners are still on the court (unless I've waited long enough and the partner is still thanking the table crew, the AD, the trainers....

2. Not knowing this rule is unbelievable to me.

Yeah, you probably handled it poorly, but only because you don't know who's within earshot. Maybe a "softer" approach would be to quietly tell him to either get back onto the court or pull out his rule book and THEN get back onto the court.