On August 21, 1911, the Mona Lisa was stolen from Paris's Louvre Museum. After the painting's disappearance, borders were closed and media coverage of the heist spread across the globe. A tip from an art thief caused police to turn their attention toward one of the country's most promising young artists: Pablo Picasso. Among his close friends was the poet and writer Guillaume Apollinaire, whose former secretary confessed to stealing and selling minor artwork from the Louvre to both him and Picasso. However, while both men were indeed in possession of stolen art, the judge determined that the situation was unrelated to the Mona Lisa's disappearance. Two years later, they would be cleared of any possible connection to the crime, when police discovered the painting had been stolen by Vincenzo Peruggia, an Italian artist who had been working at the Louvre.

Source: Mental Floss