Promissory Note Other Debt

The person holding the promissory note is the one owed the money.
That person can bring a lawsuit against those who have defaulted on the loan.
He owes your mom.
He doesn't owe you anything.
Have mom sue him, but don't expect to be doing the happy dance after she prevails.
She'll likely get a judgement, and another pretty piece of legal paper.
Then she'll have to TRY and collect on that judgment.
Your state, TN, is one of the states where those trying to enforce judgements generally don't fare well.
This is why its not a good idea to get involved in financial transactions with those you don't know well.
One good thing for you, you have a nice house, and got rid of a deadbeat.
That isn't bad, OP!

 

How is the property titled? When the divorce was processed that should have been a major factor in determining how to deal with the loan.