Not transfer the vehicle ownership

As the sale is not materialized the buyer can cancel the sale and demand return of the sale consideration amount by issuing a legal demand notice on the basis of the evidence for transferring the money by a cheque.

He can also think about lodging a criminal complaint with police before the seller approaches police for theft of vehicle 

The buyer should issue a legal notice to first owner illegally withholding RC of the vehicle stated to have already been sold by him/her.

Sir, the seller take stand that he was lost the RC book of vehicle and not supported to buyer .

The carelessness of the buyer at the time of buying the property i.e., without verifying the original RC and other documents pertaining to the vehicle can be held as an act of negligence  and irresponsibility of the buyer, thus he is now lamenting over his grave mistake.

Even now he can adopt the steps suggested, if necessary with an assistance of a local adocate to recover his money by returning the vehicle which is without proper documents/relevant papers.