About 15 years ago I found a US passport lying on the sidewalk in Tokyo one Sunday. I thought I would drop it off at a nearby police station, big one, not a koban. They did not want it. I finally volunteered to send it myself to the US Embassy on Monday from my office and the police looked relieved!

Had no way of contacting the person but did try a quick search. I am sure that would have saved him a heap of trouble reporting it missing and getting a replacement.