You said this was stolen from the shop you work at. If there is surveillance at the shop, go through the footage shot on the day it was stolen and see the face of the guy that stole it. If you have any friends that are police officers, provide them with the proof of your phone being stolen. You could always say you are interested in purchasing the phone and stake out the location you guys agree on to see if the person selling it is actually the one that stole it.
If you truly want it back, you need to invest the time to do this. Good luck!
If you truly want it back, you need to invest the time to do this. Good luck!