Mona Lisa
It was lost for two years, and everybody thought it would be lost forever. A worker at the Louvre, named Vincenzo Peruggia, had actually stolen it. He had hidden it in his coat and walked out with it after the museum had closed. He wanted the painting to go back to Italy and be shown in an Italian museum. After hiding it in his apartment for two years, he grew impatient and tried to sell it to a gallery in Florence, but was caught. It was shown all over Italy before going back to the Louvre. People thought Vincenzo was a hero who loved Italy, so he only spent a few months in jail.