what happens if the finder loses the item and the owner turns up?
The finder could be responsible for replacing the item. It's a lot of burden to put on someone really.
Let's say the ring was an expensive one, worth £5,000. Imagine losing that and then suddenly the owner turns up wanting their ring back. It's going to get messy.
Wow I'm glad I didn't think about this when I found it otherwise I would never have picked it up! Popped into the nearest bar and explained the find so they could direct anyone to the police. With it being close to a bar I too imagined a big argument followed by a dramatic ring throwing, however could easily have just slipped off.