The ruling on borrowed money whose owner is unknown

The third question in the letter of our brother Sa'd Musa al-Suwayriq al-Salahi from al-Hujrah in the land of Zahrān. He says: I previously took a sum of money from one of my colleagues at work as a loan. A decision was issued transferring me to the Eastern Region, and I have not met this person for a period of no less than ten years. Therefore, I ask for guidance on what I should do with this amount. Please inform us, may Allah reward you with good.
Answer: It is obligatory for you to ask those who know your colleague and those who are acquainted with him. You should ask those who know him by letter, by telephone, by every means. So when you find him, you send his right to him. If he has died, you give it to his heirs. You ask about his heirs and give them the right. As for if you are unable to do so and do not know his status or his heirs, then you give it in charity on his behalf with the intention... you give it in charity to some of the poor with the intention on behalf of your colleague. And Allah (Exalted and Majestic is He) will reward him for that and benefit him with it. And you are absolved after your inability and after your effort to know his location or his heirs if he has died. If you are unable to do all of this, then you give this money in charity with the intention on behalf of your brother who died. You give it in charity on his behalf, and Allah will reward him and absolve your conscience. Yes.
The presenter: May Allah reward you.