I really and truly don't think its anything to be worried about. He does NOT sound like a player, nor a BShitter. It genuinely sounds to me, that he was with his boss too, which is always a difficult thing to get away from, socially or not, you feel obliged to 'do the right thing' with/for them. They do, annoyingly have a certain hold over you - well men anyway!
I think if it's really got under your skin, then have a serious talk about it,get it all out in the open and put it to bed, draw a big fat line under it.
Yes, it was crap, yes he should have text you or excused himself and called to explain, but he didn't, and that can't be changed now.
Don't play any games with him, like not calling/ answering calls etc, its not worth it. JUst be honest and true. There's no point, and it's immature to behave any other way.
My DH has Aspergers, if he has a situation he doesn't know how to tell me about, or, something crops up, or, he cant come home as planned ( he works away mon-fri) then he simply cannot cope, does not know what to say or do,so does nothing at all ! Instead of just sending a txt or calling and saying i'll be a day late, or that he's working all weekend after all. He simply just doesnt DO anything. He'll not answer the phone, as he doesn't know what to say upon answering, as he can't deal with emotion and think I might be. Despite me never being emotional, but just wanting to know whats happening! As I do understand plans, situations etc do change suddenly, in all kinds of situations! But anyway... my point is, it really is not a big deal at all. Honestly.
Just talk, move on, and leave it behind you. Tell him it was a crap thing to do, hes never done it before- clearly is commited to you as he's mentioned living together. Do you have Dc's together btw?
Seriously, as someone who's been through a hell of alot worse, and deals with all kinds of odd stuff on a regular basis, its nothing. Its never happened before. Just let it go, ensuring he knows how you felt about it.
Move on and be happy
Put a little perspective on it you could have my DH to deal with!