What is the ruling on waiving a debt that has not been claimed by its owner, and the debtor has forgotten about it?

It is permissible to demand a colleague for one's right, but it is better to pardon and overlook the one in hardship if the claimant is well-off and does not need the money, based on the Prophet's (peace and blessings be upon him) saying: "A man from among those who were before you was called to account, and no good deeds were found for him except that he used to mix with people and was well-to-do. He used to tell his servants to overlook the one in hardship. Allah Almighty said to His angels: 'We are more deserving of that than him; overlook him.'"