Blue prints lost by GIC Housing Finance from my loan file

Dear Experts, Recently I have foreclosed my home loan with GIC Housing Finance Thane branch that was taken back in 2010. I was called in bank on 9th July to collect my original documents, but the blue print of my building plan was missing from my file. I refused to take the papers. The branch manager said will search and give it as soon as possible. Yesterday I called GIC and they said since the original is lost, they will give me Xerox copy of the blue print from builder. Since, I am in litigation with builder for his illegal construction for same building, can I believe the authenticity of Xerox plan given by builder as he can give me modified plan? can I accept xerox copy of plan from GIC since its originality and source can not be proved? Lastly can the xerox copy of blue print create any problem in future while selling the flat? Dear experts, please guide me i am in very confused state of mind.