First....did your boyfriend drink his NORMAL drink??
Second...did your boyfriend drink his NORMAL amount??
Third....did your boyfriend's DRUNK hit him ALL-OF-A-SUDDEN????
If you answer yes to these 3 questions....then I suggest to you that your boyfriend's drink was spiked with GHB, a colorless, ordorless drug....
I went to a bar...I drank 1 1/4 white russians(white russian is what I drink)......All of a sudden...I felt warm all over....Then I began to feel like everyone there was my enemy..I knew it was time to go home......I have NO MEMORY of how I got home(I drove)....I woke up 17 hours later in the middle of the living room floor----in **** and pewk......I remember hearing the phone ring....but was unable to move.....When I awoke, I felt like I had been in a coma....It was scary....It took me several days to feel normal again.....Never leave your drink unattended....If you think someone spiked your boyfriend's drink after reading this, beware of the parties you attend....
It is also possible he had an alcohol related seizure which can kill a person.
What he experienced is not uncommon for someone who is extremely intoxicated. The reason he doesn't remember is that he likely was so drunk he was having a "blackout" which is a very dangerous condition. Whether this is a one-time thing depends on him. If he continues to drink so much it will likely happen again. It wouldn't surprise me if he has a problem controlling his drinking.