1. IF AT ALL, the original Sale Deed is not traceable (for any reason, whatsoever ....) in House or at SRO, THEN get a "Police Report" of the same, stating facts, that it is lost /misplaced /stolen /whatever....
2. ISSUE proper Public Notice in two local Newspapers, thru a registered Advocate.
3. Execute a "Irrevocable Indemnity Bond", in favor of Buyer-party, indemnifying buyer against ANY & ALL losses /claims /whatever...., of any kind whatsoever & whichsoever.
4. Armed with above documents & other existing available society documents, execute proper Sale Deed with confirming & consenting signatures of ALL residual legal heirs. PERIOD.