What is the fate of money you received on behalf of a colleague at work, of which he is unaware, knowing that you did not receive it yourself and you do not know the whereabouts or phone number of the original recipient?

You must strive to search for the owner of the money to return it to him, as it has become a trust upon your neck. If you exert your effort and do not find him, you have a choice between two matters: keeping it for him until he is found, without guaranteeing it if you have not been negligent, or giving it as charity on his behalf. If you find him later and he approves the charity, your responsibility is cleared. Otherwise, you must pay it to him, and you will still have the reward for the charity.