So what happens if someone (a loseproof member) finds the items but decides not to return it ?. It can help muggers too , why the need to mug someone directly,

So what happens if someone (a loseproof member) finds the items but decides not to return it ?. It can help muggers too , why the need to mug someone directly, become a loseproof member and you will get to know the approximate location of the item. And then he looks for it for a day , finds it and sells it .