Car ownership is not transferred by buyer into his name.

Hello Sir, I sold my car back in 2012 when i was in pune and the payment was made in cash. and buyer had agreed to transfer the vehicle on his name but he didn't do so till now. now one day he called me asking for my RC xerox as he states that he lost the document after 4 years. Can we get his consent on bond paper mentioning that from the time and date of the sale whatever has happened till now is his responsibility and he had lost the paper hence could not transfer ownership into his name? the stamp paper would have current date and the sale has happened in the past, will