If I sell a car, can I be held responsible for any citations on the car after the sale?

In 2004 I sold a vehicle. Now here we are 7 years later, and I'm trying to renew my license and the RMV is stating that I have a $250 citation for vehicle abandonment from 2004. Apparently the guy I sold the car to never registered it in his name, so I was the last known owner which is why they issued the citation to me. I no longer have the bill of sale or any contact information for this guy. Am I going to be held responsible to pay this citation even though I sold the vehicle 3 months before the citation was issued? Is there anything I can do to fight this? I have no idea why this is coming up now as I was able to renew my license in 2006 without any problems. I don't know what to do and I definitely don't want to pay a citation that doesn't even belong to me. Any advice?