Is it permissible to take a flash drive found next to a garbage bin and sell it, and if it is not permissible to take it, what should be done with it?

There is no objection to taking a flash drive or other items that their owner leaves behind out of disinterest. Scholars, in the chapter on lost property (Luqata), have stipulated that if someone finds an animal that its owners could no longer manage and thus abandoned it, and he takes it and revives it, it belongs to him. Similarly, whatever is thrown into the sea out of fear of drowning becomes the property of the one who retrieves it. It is even more so if the owner discards it out of disinterest.