Having been a golfer for the better part of 40 years I really haven't run into a problem like this often. We were taught to put our pitching or sand wedge or whatever we used for the approach shot on the green in the direct path back to the cart or cart path, whether walking or riding so we literally would have to almost trip over it. Most people do pull two clubs for their approach shot.
Most people who find clubs pick them up and put them in their bag. Sometimes at the end of the round they forget they are there in the business of adding up scores and paying a side bet, thanking someone for a nice round etc.
Most people have a matched set of clubs and have no need for someone else's wedge or nine iron because it isn't right for their height or game.
I don't think many are taken and kept on purpose.
Sometimes a golfer who picks up the club finds the club only after he returns home in another state too.
