I'm told that in northern Europe you could leave your laptops or whatever in semi-public places (like, cafès I suppose), and if you come back after a few hours it would still be there.
Can northern Europeans confirm or deny this?
You can usually ask someone to keep an eye out while you go to the restroom/refill coffee and most people are happy to help, but you need your due diligence
Where it is not true is in large cities. Small cities and rural areas are one of the safest places on Earth as long as you don't get nibbled by a moose or overrun by ants.
Where I'm at when people (like, taxi drivers) do bother to return lost-and-found wallets, it's newsworthy enough to make its way to the newspaper.
That should tell you the status quo here.