most thieves wouldn't bother returning a "fake" they'd throw it in the nearest trash. Thieves are not conscientious people...
I'd be interested in in how they opened a locked locker? If you had to unlock it to get back into it, it had to have been someone with a master key, possibly management themselves...just sayin'- maybe cut open a tennis ball on a seam and use it as a 'hiding in plain site' jewellry safe at the gym?