Lost and Found
The con should have a Lost and Found (Lost Property) office, or coordinate with the hotel to use theirs. Put it in a place that is easily found, and make sure that location is prominently publicized to the members. People will often walk off and leave bags or parcels, only later realizing they are missing something valuable. In a similar fashion, people will find seemingly mislaid items and have no idea what to do with them. Make it easy for these folks to solve their mutual problem.
At the end of Con, you may end up with a treasure trove of someone else's worthless junk. The Con should either plan to turn these over to the hotel, or come up with a way to charitably dispose of these artifacts. Publicize the policy, so your members will know what eventually became of their missing knack-knacks and foofaws.