Transfer of ownership

I have selled my bike to an dealer in exchange of new bike purchase 2 years earlier. that dealer had provided me only delivery challan on which it is mentioned that the agency is liable for any accident, mishappening from date of purchase till date, i have asked them to sign and stamp a affedavit but they denied and they told me that they had provided delivery challan and stamp and signatures are mentioned over there with vehicles details. the agency had selled the bike to outside biker dealer and that dealer had selled bike to unknown person from date of selling vehicle till date buyer didnot transfered the ownership to his name. the buyer had get all form and paper work signed by me for transfer purpose but till date he had not done so. when i approached the dealer they ( from where i have exchanged my bike) they sended me to outsider dealer and when i approached him he said i will inform buyer regarding this but still no action taken by his side the bike is sounding in my name. again i approach him (dealer) he said no worries the delivery challan is with you nothing legal will happen against you and you are not liable for anything mishappening. the delaer is still not providing details of buyer. please help for the same.