number directly with the court it is filed in to see if it actually exists. If there is a case, you will probably want an attorney. Only liability I could see would be an undisclosed issue that caused an accident, but usually cars are sold as is on trade ins, so even that is a stretch. Do not contact any of the contact info provided in the letter. Just the court. If there is a real case, an attorney should do any further contacting.

But, my money is on scam.