Oh my, you'll never guess who had O'beirne's papers and diary- OTTO EISENSCHIML!!
Below is a footnote from his book "Why Was Lincoln Murdered?"
8 O'Beirne papers � A collection of documents left by Major
(later General) James Rowan O'Beirne, in possession of the author.
The papers also include a diary kept by O'Beirne
while the pursuit of Booth was in progress,and some letters of Captain Beckwith
http://tera-3.ul.cs.cmu.edu/NASD/d23d381.../6748.sgml
Could Carnegie Mellon U be in possession of Otto Eisenschiml's papers?