Yesterday in Boston we found someone's keys in the public garden, near the pond with the swan-boats. The key ring had a card for a gym, with a phone number. I called the number, read them the card's number and they looked up whose keys they were.
As they had only an email for this man, not a phone number, we had to figure out where to leave the keys so he could get them later. Across the street was the Four Seasons Hotel. We took the keys to their desk to be kept in their Lost and Found, gave the hotel staff the name of the man whose keys they were, and gave the gym the phone number of the hotel so they could email that to the man who owned the keys.
Today I received a phone call from the owner of the keys. He'd gone to his gym this morning and had been handed a paper telling him his keys (which he lost while out for a walk Saturday) were at the Four Seasons. He called to say thanks.