Continuity mistake: In this episode, Darrin announces that he doesn't like cream in his coffee. In season 2, "The Joker is a Card," Darrin likes cream in his coffee, and Uncle Arthur zaps a cow into the living room.
Other mistake: In the opening scene, Endora disappears then reappears for Tabitha. If you watch closely, just before she reappears you can see the shadow of Agnes Morehead/Endora on the wall behind the couch quickly coming back to the couch for the camera cut to recapture her.
Answer: Larry had been telling Darrin what it means psychologically that Samantha gave the coat away. Larry said giving it away meant she's happy being married but if she liked the coat it means she desires to be single and carefree. So when Darrin sees the coat, he immediately thinks Samantha doesn't want to be married and the fact that she twitched it means (in his mind) she wants to be a single, carefree witch again.
Bishop73