Put $100 cash dep on car from private seller...called the next day asked for $ back. Nothing signed by me?

They wrote me a handwritten receipt for the $100, but I signed nothing. Called the next day to tell them I had found a newer car for less money, so I wanted my money back. They got nasty and said "no way". I was told by a car dealer that in VA they can't keep a deposit if the car is not bought. What recourse do I have, if any?