You might be on to something here..
I mean I wouldnt? I've def done that and had that done to me. See a friend of mine heading to the bathroom and thinking I'll scare them on the way out? Has no one else ever done that? Me and my friends basically chat about our day in the bathroom. It's about as regular a meeting place for us as a classroom.
You don't really have the right to be angry if someone walks in on you while you're having sex in a public bathroom. Plus, they were all equally embarrassed, so as friends you laugh about that and move on.
Somehow I don’t like his friend to be honest. I don’t like them since they followed him to the toilet. If it was me, I would feel angy and uncomfortable. They are quite carefree.