I went through this same thing a couple months ago. Found an iPhone 6s plus. The service had already been turned off so I opened the sim tray and saw it was a TMobile sim so I went to my local TMobile corporate store. They called 5 different contacts from the account since it was a family plan (they would not give me any numbers obviously) and left voicemails with my personal cell number. No one contacted me. Kind of amazing someone wouldnt want their phone back even if they already bought a replacement.
After a week without a call, I dropped it off at the local PD. I would imagine its still there lol
After a week without a call, I dropped it off at the local PD. I would imagine its still there lol