Board Thread:General Discussion/@comment-6036560-20130318104316/@comment-4260948-20130425020035

Kurt, I believe, may have left storybrooke right after Owen, but lost his memories when he crossed the town line.

We know the town line has some effect; Greg crashed in arriving after all and he'd been INSIDE the smoke that brought the curse and inside the town, so may have been affected.

If he was affected (which caused the crash) then Kurt could easily lose his memories crossing over the town line, which is why he never went back for Greg.