Deceased father mortgaged property papers, cant find it now,what to do

I recently applied for gun licence under family heirloom to inherit my father's gun after his sudden death. Mine is a family of farmers. Some of my friends told me to attach agriculture land papers (Bahi) to increase chances of licence approval as process is same as new licence and it can be denied for no apparent reason. Now problem is, after my father's sudden death we came know that, he had mortgaged the property papers in bank against loan as told by one of my relative, but we still don't know about bank and branch and we don't even have xerox. Now my question is, Can I use an affidavit instead of papers and if yes, what should I mentioned? Will it be legal? Does it stand valid? Plz advise...thanks in advance.