How can one rid oneself of the rights of people that one might have forgotten or is unsure of, especially since asking them might not be beneficial?

The fundamental principle is the absolution of one's liability (bara'at adh-dhimma). As long as you do not recall having a debt and no one has demanded it from you, then nothing is incumbent upon you. This is because the fundamental principle is the absolution of liability until its encumbrance is proven.