Responses
I think that flashback was for the new "past" and we will see it later on before he comes back to the present.
Maybe in the original past they were roommates just for a little time before ML had success (and cuz MC was working all the time they didn't have a lot of time together)
quite strange they're not that young to forget something like that, like in the flash backs they seem to be quite intimate.. or even one of them should remember something? or maybe they had a car accident or something