Problem: Buyer is a regular attendee at garage sales in her town. While at a sale at the home of Seller, Buyer sees a rather dull and dirty landscape painting in a rather gaudy modern frame. Buyer, who thinks that the colors in the painting would go well in her living room (once the thing is cleaned up) offers $50, and after some negotiation she and Seller agree to a sale at $85. The painting is subsequently proved to be a lost painting by American luminist artist Sanford Robinson Gifford (1823-1880). The Sotheby's auction house appraises the painting at $100,000 to $130,000. At no time prior to the sale was Buyer aware that the painting was a Gifford. Immediately upon learning of the identification, Seller sues to rescind the contract on grounds of mutual mistake. What result and why?