Overboard/Fridge

Fridge Logic

 * When Joanna finds the monogrammed "J.S." panties in Dean's glove compartment, she assumes he's having an affair. But Joanna had seen the panties before, after losing her memory. She was actually wearing them when she went into the drink, and when Dean comes to pick her up, the police offer shows them to Dean and comments that "she didn't know what the initials meant". ("She wouldn't, 'cause I bought 'em for her at a garage sale.") Shouldn't she have recognized the panties from before?
 * Not necessarily. She may have put most of the time at the asylum behind her, especially if she was still in a confused state at that point.