Letters by Hemingway, F. Scott Fitzgerald and Morley Callaghan were stolen from a Toronto book dealer in 1993. these letters are now estimated to be worth $1 million and the dealer believes they are still out there.
The letters discuss one of the most famous fights in literary history (are there many?) — a 1929 boxing match in Paris between Hemingway and Callaghan, during which Hemingway was bloodied, then knocked to the mat. http://ehto.thestar.com/marks/the-curious-case-of-the-stolen-hemingway-letters