>>150968264 (OP)
The answer is whatever's funnier.
Pim is presented as the most earnest and naive of the Smiling Friends, while also being the oldest compared to Charlie and Alan, who act more mature. Him being a virgin on top of this just adds to how "pathetic" this character is in the show's world.
He's the kind of guy who's never had sex, always carries that "maybe some day with my soulmate" hope in the back of his mind, and then finally manages to score while on a Charlie/Mr. Boss-induced Vegas bender, remembering absolutely nothing about it after the fact.