Twice, I saw them -- resting on the bus stop seat -- forlornly. Both times, people were sitting respectfully about a foot away from the keys, with expressions that said "Nope, not mine." The first time, at the bus stop near the Zion Road food centre, it was a singular key with no chain or anything else attached (looked to me like a house key, oh dear). The second time, at the bus stop near my house, it was a bunch, including something that looked like a key to a cabinet.
What do you do with them? Take them to the nearest police station? But would they find their owners? I had vision of the police testing the key on all the households in the vicinity and finally exclaiming, "Aha! This one fits! Yoohoo, come and get your lost key, ye occupant of the house!"
Maybe should take the key and place an ad in the papers: "Please claim your key from.... Found at..."
The elderly couple who was seated at the Zion Road bus stop said wisely, "Leave it here. The owner may come back and look for it."
Anyway, it is always better to lose a key than to lose a wallet. You can always call the locksmith. Some are on service 24 hours. But they charge a bomb.