Last November, a work titled Potiphar’s Wife by British painter Euan Uglow appeared in a private sale by Christie’s in London. “We were all so excited,” says art historian and curator Catherine Lampert. “I had tried many times to find out where that picture was.” It depicts a woman lying on the ground against a blue wall, legs crossed and arms stretched out behind her to, it seems, stop a man in a T-shirt from leaving. Both cling to a beautifully draped length of orange cloth. This is the last painting Uglow talked to Lampert about as he lay dying...