Is it a condition for "the permissibility of benefiting from a small amount of money that its owner does not care about" that the owner of the money be unknown?

If you find something and you know its owner, it is not considered a Luqata (found item) in the legal sense, and you must return it to him. One who sees another's property exposed to loss or damage and does not strive to save it commits a sin, because preserving another's property is obligatory when one has the ability. Scholars have differed regarding the obligation of guarantee upon him if the property is damaged or lost due to his negligence. The majority are of the opinion that there is no guarantee upon him, while the well-known view among the Malikis is that guarantee is obligatory upon him.