FWIW, if I were the recipient of your low-value item, and its rightful owner showed up, I would return it without any issue. I think after 2-4 weeks, you're probably safe.
(As a parent in a fairly well-to-do town, I am always amazed at the expensive articles of brand-name clothing which are in the lost+found at school. I'm also amazed that my kids stuff when lost does not always appear there... The point here is that for a low-value item, I don't think many people expect or try very hard to get it back.)
Tim