What should I do about a debt I cannot repay because I cannot find the owner?

If a person borrows money and does not know the whereabouts of the creditor, he must inquire about him. If the creditor has passed away, he should pay the money to his heirs. If he is unable to reach the creditor or his heirs, he must donate the money as charity with the intention that its reward be for the owner of the money. If the owner of the money appears and approves of the charity, then that is sufficient. Otherwise, he guarantees his money to him, and the charity becomes his (the borrower's). Any money whose owner is unknown, such as usurped property, deposits, and money belonging to thieves, should be given in charity and spent on the welfare of Muslims.