Morale of the story... many people don't know how to throw a punch properly. And hitting someone in the head is a really bad idea.
I would like to add to this, throwing a punch at someone while there is a solid wall behind them is a bad idea. my g/f and I were play fighting (we're both martial artists so we fight much like what was in your story). she goes to throw a strait punch to my face and I bob out of the way, we were a bit close and she over extended, hitting a solid door frame in my kitchen... didn't break anything, but her knuckle had a decent indent and she had trouble using her hand for like 3 or 4 weeks after that, lol