Corrected entry: In the scene where Patience visits the jewelry store to discover that it is being burglarized she sneaks up on the burglars from the second floor. She uses a temporary mask. When the fight is over she returns it in one of the broken displays. The displays are on the ground floor. She cannot possibly get the mask without breaking the shelf where it came from and not being spotted by one of the burglars.
Andreas[DK]
6th Jan 2005
Correction: The showcase with the mask is in fact on the second floor. She exits the same way she got in and puts it back on her way out. Before entering the store Catwoman sees one of the thieves on the second floor so it is very possible that he and not Catwoman smashed the showcase.
Andreas[DK]