being friends should honestly not have anything to do with being a client. if he doesn't show up for an appointment, I'd still charge him. Tell him it's your business, and you keep a tight schedule. believe me, if you let him off the hook (unless he has a very good reason for not showing up), he'll most likely do it again.
it's a freakin business apointment, not just for hanging out. If he were a good friend he wouldn't waste your time like that.
running your recording schedule correctly is not being an asshole, it's being professional.
that being said, same thing happened with a friend of mine and myself. I couldn't make it due to being hungover, and he charged me. I had no problem with that, it was my stupid idea to go drinking before a recording session. If I had something important to do, like a sudden death in the family or whatever, it wouldn't have been a problem, but waking up too late and making an appointment on a day where you don't have enough time is irresponsible and childish. Be polite and nice, yet firm. Let him know you're not bullshitting, that he needs to take his appointments seriously, and charge him.