Lost Original Property Documents

My father has some properties under his name. He has recently passed away. After his death, I don't know where he has kept original property documents. Recently, I got a call that someone possess a sale agreement along with father signature, original documents, etc., he demanded 9L. I have complained in the police station for the return of original documents.. but, police suggested to transfer the property to some other name.. is this the only solution. They are approaching third-party to sell the property.