Quote Originally Posted by Radar View Post
It's been months since Sam attended the card tournament in particular and probably the comic shop in general, so that people would be less likely to notice his transformation. There was no reason for Sam and Sarah not to meet in that time - at least no reason after they talked about te transformation magic secret.
Strictly, we don't know they have talked about it. They might have done during the timeskip, but Sarah figured it out during the party from Grace's various panics rather than because Sam told her.