Do I have a right to personal property left behind in the house I just purchased?

I purchased a home 2 years ago. The owner left a large painting in it. First she had asked if I could hold on to it for a month. Then she tried to sell it to me. When I declined, she said I could have it. A year and a half later with no other contact previously, the former owner asks for it back, saying she's sold it to a gallery. I said, you gave it to me and its been too long so you can't have it back. Now the gallery is suing me and saying the painting is theirs because they purchased a whole group of her paintings. Who is in the right? Or should I say, what are my rights? There is nothing in writing or the closing regarding this painting. Thank you.