When a person does something outrageous while inebriated, then dosen't remember it the next day.
You were so wasteds you almost got in a fight with a guy twice your size! You wouldn't stop hitting on his girlfriend! You got damnesia, because I was like DAMN when I saw that!!
When a situation follows with: Damn! That didn't happen or damn! I don't remember that; usually after copious amounts of alcohol, due to having done something regrettable that someone reminds you of the day after, that you don't remember.
You came onto me last night! Damn! I don't remember that. Must be that damn, damnesia. I suffer from that, sorry.