Last July, a Hilton Head resident who was downsizing contacted Master Appraiser Llewellyn Dykes to ask if any of their artwork was saleable. They offered to sell him one piece in particular for $15,000.

Dykes determined that the painting, which hung over their couch, was “Diana and Callisto,” a 200-year-old masterpiece by Italian master Gaetano Gandolfi. Art scholars only knew of the painting’s existence through an 1895 archived photo stored in the Louvre Museum in Paris. It had been missing more than 100 years.