here's what a friend told me. It won't stop them from taking the camera but it will help get it back. Take a large piece of poster board and a magic marker and write the following message on it.

"To whoever is developing this film: Please ask for the I.D. of the individual who brought this film in. If it is NOT (enter your name here) then this camera is STOLEN so please contact the police and call me at (enter your phone number here). Thank You.

Once this message is written out in full take a pic of it. When he goes to get the film developed he'll be done. They should also card you when you take it but at least you'll have the proper I.D.