IDBI Bank — house property documents went missing from bank

Address:

Thane, Maharashtra, 421301

I had taken an education loan from IDBI Bank and had kept my parents house as a collateral security with IDBI Bank. I have now repaid my loan amount in total and was expecting all the documents to be released from IDBI Bank.
We got the other documents that was submitted but we did not get back the house property title original document.
An official from IDBI Bank said that they have lost our house property document. Its the responsibility of IDBI Bank that they should have secured the property document with them. How irresponsible of them. We are really worried about it.