Hans figured it out because of the napkin that was left behind with her name on it (the slipper helped too, but wouldn’t necessarily have given her away specifically). But those details are believable enough, since with her being shot in the leg, and with a need to get everyone out of there as quickly as possible before anyone else showed up, Aldo and company didn’t have time to comb the place for stuff that might give them away before leaving. Remembering to look for that napkin with her name on it would not have been something that came to mind for her in that situation.
