'High on the list of suspects, thanks to the word of an art thief not involved in the heist named Joseph Géry Pieret: none other than Pablo Picasso and Guillaume Apollinaire. Confessing to his habit of purloining small items from the Louvre, which then took no great pains to protect the cultural assets within its walls, Pieret informed the police that he had sold a couple of small Iberian statues to a “painter-friend.” Pieret, writes Artsy’s Ian Shank, “had left a clue — a nom de plume in one of his published confessions, pulled straight from the writings of avant-garde poet Apollinaire. (As police would later discover, Pieret was in fact the writer’s former secretary.)”

https://www.openculture.com/2019/01/when-pablo-picasso-and-guillaume-apollinaire-were-accused-of-stealing-the-mona-lisa-1911.html