malice or distraction?

Hi, this is my first post so here goes. I've been with my boyfriend for a year and he has ADD. He's really insecure and has a few anger issues but they're pretty rare and only once has it been directed at me. But last night we went out with friends, got really drunk and jumped on the bus back to his house. As usual I fell asleep on the bus but this time when I woke up I was alone and about 45-50 minutes out of town. I called him like why am I alone in a strange town, where are you and he screams at me that he's at home, he's not responsible for me, its my fault and so on and on. Today he says he can't remember anything and that the only thing he can think is that he fell asleep too, woke up and just forgot we had been together. What I can't figure out is if this is probable? Could he just forget about me and the shouting was a defense mechanism cos he knew he messed up or did he mean to leave me on that bus?