"Kin'emon's brat," Zoro shot back, "the one we picked up on Punk Hazard. You really don't remember any of this at all?" It was starting to sink in - sort of. He still couldn't fathom not being in the New World at all, but clearly something was very off. Sanji, at the very least. "Did you get hit in the head and lose two years of memories?"

Yes, that had to be it. Somehow he lost his memory and decided it was two years ago and he needed to shave. Made total sense.