Generally the original Promissory Note is essential to sue as a Promissory Note, but the lender can still sue and either (a) include a count for Lost Note and reestablish the note, or (b) sue simply under the "Money Lent" cause of action. So even if you did not deliver the originally signed note, the lender can still go after you for the money owed.
Answered on Feb 10th, 2015 at 1:49 PM