I am a mortgage lender and own a real estate company. This comes up all the time.
All they have to do is go back to the attorney/title company that refinanced their last loan (2004) and get record of the filed satisfaction of mortgage.
Also, like another poster stated, it could also be a HELOC or creditline that is not being used with a zero balance but is a lien on the property for the credit limit.
Chase will respond to the title company or attorney so it is a good idea to have them call on thier behalf as a third party.