Our daughter fell on hard times and had a car repossessed in the state of Indiana more than 7 years ago but less than 10, I do not have the exact date. The car was sold and I know she had some paperwork about it but I don't remember much about it.
Three years ago she married. She and her husband live in another country. One of the things she needed to do in order to have a permanent visa was pay off any remaining debts and obtain a police and FBI clearance, which she did. The matter of the car never came up, maybe it was forgotten, it certainly never was pursued anytime I can remember.
Now, fast forward to yesterday. A letter came in the mail addressed to her. Now, let me make it clear, she told us to open anything that was addressed to her, so we did. We found a mysterious and serious letter stating that she owed $15,000. We later discovered that it was from a debt scavenger.
However, before we knew that, we called to find out what it was about, because the letter did not state what the debt was for. We were told that there was something like $9,000 worth of interest added to the balance due after the car was repossessed and sold. We told the guy that our daughter didn't live here anymore and that she did not owe anything. He tried to say she was dodging the requests to pay but we said no.
We did not offer any other information. Today he called again and demanded that our daughter or her lawyer (?) call by noon tomorrow regarding a court case number which he gave me.
Now, I have been reading everything I can, but my husband does not want me to be concerned about it. He does not want to worry our daughter and son-in-law so he does not want to tell them about this. If they knew they might be so worried they would try to pay.
My questions are:
(1) Should I be concerned? Our daughter does not hold any property here in the USA, in fact she does not hold property in Australia because she is not yet a citizen. But is this something that is not going to go away?
(2) The letter says that if it is not disputed within 30 days they will assume the debt is valid. We did not agree to anything. Our daughter is not here and has not agreed to anything. Did we cause problems by calling? We are changing our phone number and having it unlisted, so any other correspondence will be by mail. Should we return it unopened? Can he take the fact that we called and use it against our daughter?

Please help!
Thank you in advance.