Sale deed lost by Sub registrar

Thanks for your the valuable information shared with the public.The whole blog is really informative. I have a similar but a bit different case wherein after the execution of sale deed , the acknowledgement receipt was kept by the bank(India bulls finance limited) as they had to collect the original documents from the sub registrar's office. Mean while after after a month of registration, they told us that the sub-registrar is not giving the sale deed and it seems that the registrar has misplaced it. Also, the original acknowledgement receipt is with the bank. We also approached the sub registrar wherein he conceded that the our original copy of sale deed is not traceacle. Also, he gave us the true copy and gave us a letter stating that it is still under search. Adding to that, the bank has sent us a loan recall letter after 8 months without taking any action on this issue for so many months stating that since we were supposed to submit the sale deed to them (inspite of having the original acknowledgement receipt with them), we are at fault and we should pay all the outstanding amount. Kindly suggest what should we do.? Shall we send a legal notice to bank for negligence. We have already submitted a written complaint to sub- registrar stating all this and taken a receiving from the India bulls. Will registring the property on my brother's name and then giving it to bank be a win win situation for both me and the bank as my brother is a co borrower in this case? Kindly suggest an easy yet long term solution.