If a person stole an item without knowing to whom it belonged, and several people claim that it belonged to them, to whom must he return it?
Consider the example of a wedding guest who had to leave briefly, and before leaving he went into the coatroom and took somebody's umbrella, with the intention of returning it when he arrives back at the wedding. In the end he never made it back to the wedding, and so he hung signs in the area with his contact information in the hope that the umbrella's owner would come forth. If five people call him and claim that it was their umbrella, to whom must he return the umbrella?
The Shulhan Aruch rules (Hoshen Mishpat 365:1) that if each person advances his claim confidently and is prepared to swear that the stolen object had belonged to him, then the thief must compensate all of them. He must return the object to one person and pay the others its value.
This applies to stolen money, as well, such as if somebody leaves the office late and, realizing he has no cash, takes a $10 bill he sees on a coworker's desk. The next morning, several different people in the office claim that the bill might belong to them. The thief must give $10 to each one of them.
These laws underscore the gravity of theft and of borrowing items without permission, which is legally equivalent to theft. One must ensure never to take an item belonging to somebody else without receiving expressed permission from the owner.
(Based on Dayan Shelomo Cohen's work "Pure Money," vol. 1, pp. 44-46)
Summary: It is forbidden to borrow an object without receiving permission from the owner. If a person steals an object or borrows an object without permission (which is equivalent to theft), and several different people claim that the object had belonged to them and are prepared to substantiate their claim to this effect, he must compensate them all. He returns the object to one of them and pays the others the object's value.