Lost deed of apartment

Dear Experts,

I am owners of a 2 BHK flat in pimple saudhgar, pune for the 2+ years, which I am  trying to sell.

I have a HDFC home loan, The buildings have been registered as "Apartments" and not "Society", so each individual flat has a Deed of Apartment in addition to the other legal documents.

All other documents are in order, except "Deed of Apartment", which I have lost during travelling somewhere. I have also lodged an FIR for the same

I have a buyer who is ready to purchase, and he is taking LIC loan, now  I have already obtained a "certified copy" of the said document from the sub-registrar's office (sealed, stamped, and signed), which has been refused by the bank for processing loan, as this wont work with a quote  "Yeh to koi bhi jaa ke nikaal sakta hai").

Kindly advise.