What is the ruling regarding someone who is owed money by a person whom it is impossible to contact or meet after a long separation between them, and what should be done in this situation?

If a person has a right over an absent individual and cannot contact them, they must refer their case to the judge or whoever is in a similar position, because they are the ones who look into claims concerning financial and other rights over an absent person. Whatever is proven before them, they act accordingly.