I have had mixed experience. Used to play at a club that was private and had virtually no outside play. If you lost something and someone found it, you could pretty much bet on it being turned in. That same club fell on hard times and eventually became a very popular public course. Since that time, it is rare that people turn in anything of value. Club covers, yes. Towels, probably. Clubs, almost never.
I had one experience that really left me with mixed feelings about a different course. I played at a course that I rarely ever play at. I left my GPS in the cart (I really wish golf related devices would come with a case color other than black. Black just blends in completely with the pockets you find in golf carts. Black case, black liner in the golf cart compartment. Just did not realize I had left it. When I got home (75 miles away) I realized I had left it. I called the golf course and they told me nothing had been turned in. They took my name and phone number. The next day, the golf course calls me and tells me the GPS was turned in by one of the cart boys. I drove back that afternoon to pick it up. I thanked the guy in the pro shop and told him if the young man was there, I would give him a tip for doing the right thing. He told me the cart boy had lost his job because he took the GPS home and then turned it in when he came to work the next day. I felt really bad about the whole situation. Guy in pro shop told me all the cart guys had been warned about doing such. Still does not sit right with me today.