Well, the theft may have occurred more than a century ago, but it's still unsolved. Barbara Schmidt posted the following to ExLibris this afternoon:
"On July 11, 1907 a briefcase/suitcase was stolen in Grand Central Station in New York from Albert Bigelow Paine, the author of MARK TWAIN: A BIOGRAPHY. Scholars believe the briefcase contained the bulk of an autobiographical manuscript of Orion Clemens, the brother of Mark Twain.
In spite of offers of a reward at the time and even an appeal in 1940 from Bernard DeVoto, then editor of the Mark Twain Papers, the lost manuscript has never been recovered. I have written a short article about the lost manuscript and am posting the information to this list in hopes that some archivist or collector may have come across information that would lead to the recovery of the manuscript if it has, in fact, survived."
Schmidt's article, "The Lost Autobiography of Orion Clemens," can be found here, along with her contact information. If anyone out there knows something about this manuscript, I of course encourage you to be in touch with Barbara Schmidt. You could help solve a mystery.