OT - How old is he?!

Next time he has his headphones on in public listening to music ask him to text you so the others in the room don't hear anything. Tell him it'll save him from an embarrassing encounter.

If i'd have been there when he got out of the bathroom i'd ask him if everything came out ok? That way he would know he'd been heard and maybe it would embarrass him somewhat so he'd be more careful.

Just an idea.