Der Spiegel reveals that Steve Martin got caught up in the now infamous Campendonk forgery ring and took a loss on a painting that is now labelled a fake:

According to investigators at Berlin’s state criminal police office (LKA), the art lover purchased what he believed to be a 1915 work by the German-Dutch modernist painter Heinrich Campendonk. He bought the colorful “Landschaft mit Pferden,” or “Landscape With Horses,” from the Paris gallery Cazeau-Béraudière for what would have been considered the bargain price of an estimated €700,000 (around $850,000 at the time) in July 2004.

German Art Forgery Scandal Reaches Hollywood (Der Spiegel)