Vicarious Liability in Automobile Accident

In Feb 2012 I sold my van. My brother was there watching the transaction from inside the house. That day, I cancelled my insurance. 2 months later, I moved from WA to NY. In Feb 2013, I got a letter from an attorney in Seattle stating I was being sued because this man who bought my van hit someone in May of 2012. He never registered the van and now he won't respond to the letters from the attorneys. I received a summons and complaint in the mail (not certified) from the plaintiffs attorney stating because the van was in my name I was responsible for their clients injuries. I answered the complaint saying I sold the van, I provided the copy of the bill of sale, a statement from my brother saying he was there when the van was sold, a copy of the email from the guy who bought the van when he inquired about it. I got a letter from the plaintiffs attorney saying because I had not reported the sale to the state, I am responsible. I'm on SSD. I make 977.00/mo. I have no $ to go to WA