In Illinois, the rule is 30 years and new ownership.  I take this to mean a transfer of property via warranty deed with an insured mortgage of a sufficient loan to value to infer that the old mortgage was not assumed by the new owner.

In your example, I would continue to show the mortgage.  Even if it seems obvious that it should have been paid, the borrower will have to deal with it at some point.  Better now than when they try to sell the property.