Citi bank lost my origional house registered paper.

Location/place: Kharghar Navi Mumbai

Name of company/service: Citi Bank

Hi, I have taken Home loan from Citi bank and submitted my original registered copy to them.
I have paid their full payment in march 2011 but still not received my original copy of house, they are saying that they have lost it and done single party registeration but not ready to do re-registration for my house. if somethings happened tomorrow and I want to sale my flat and the purchaser is accepting the copy then what I will do.
Please suggest and help me in getting my original paper from Citi bank.
Because of these things I am having many problem and not able to concentrate on my Job.