In 1990, my father took out a parental student loan for my education. I do not think the loan was federally insured, but I do not know for certain. My father was the borrower. My mother was not, and I was not; neither were we cosigners. A fee was taken out of the proceeds for life insurance protection for the loan. I started making monthly payments. My father did not make payments. In 1991, my father died. I submitted the death certificate to the servicer and referenced the life insurance. I stopped making payments. The servicer did not contact me.
In 2001, Sallie Mae contacted me asking for repayment. I was confused, since I have a loan with the US Department of Education. I thought Sallie Mae was asking about that loan. It took a year to figure out they were asking about the loan from 1991. Their representatives were nasty and rude, but I did not pay. I asked for proof of the debt, but it was never provided. Last week, Sallie Mae ran a credit check on me. The loan does not report on my credit report, but Salle Mae still claims I owe the money.
What do I do?
I agree with the other poster, you aren't responsible for this debt. Now would be a good time to gather any documentation you might still have though, just so you know that you have it. There's a process for dealing with old debts that's been gone over many times in the Rebuilding Your Credit forum. It involves asking for proof of the debt (as you've done), and then following up with letters to remove the information from your credit reports and stop the debt holder from contacting you. I'd poke around over there for templates and more information.
Is Sallie Mae harassing you? If not, and it's not on your report, you could also just go with "let sleeping dogs lie" and just hang on to documentation in case they ever do try to report.