Mother deed originals 1 paper missed

Hello Everyone, My mom bought a land through power of attorney document and registered a sale deed in her name on 2008. Now we are planning to sell the land and the land was sold (sale deed) on May 2022. The registration was completed. After registration completed, now suddenly the buyer mentions that one paper is missing in the mother deed (power of attorney document - last schedule paper). Remaining documents are proper. Because of this paper missing, they are holding the final amount after registration and asking us to register a police complaint and give the 'No Trace' certificate for the missing one paper from the power of attorney document through which my mother bought the land. Actually we have all the xerox copies of the power of attorney document there with all the papers, but they claim that they need the paper or the police no trace certificate. They are not interested to have the xerox copies. Please advise what can be done and where to register the complaint to resolve this issue.