Transfer Of Motor Vehicle

I had a bike(unicorn) which I sold through an agent who promised to give delivery challan and transfer certificate from the buyer..the buyer he sold has a shop where he sells and buys bole to earn profit..so I gave 2000 commsion to the agent and sold my bike ..I got full money but I don't have any proof from the buyer it's been one month now..when I asked the buyer to give transfer certificate Xerox he tell it would take more time to sell..if you want you can return money and take back bike..but I need to go out of country so taking back the bike and finding a new buyer is not option...for me. he has a delivery challan where he took my signature..of giving me money ..so what I can do to get proof from him..cause he is very rude now..and only thing finally he tells is take back your bike..when I ask the agent he just gives fake promises of getting the challan from him..the bike is on my dad's name so I just want to be on safer side