His quest began in 1996, when the former legal secretaries of Robert Kempner, a Nuremberg prosecutor, suggested the museum contact the lawyer's two sons about donating their father's papers. Kempner died in 1993 at age 93. He had amassed a huge collection of documents from a career that included helping to convict Hermann Goering and other Nazis of war crimes.

The legal secretaries made no mention of the diary, but Mayer, then 46 years old and the museum's chief archivist, suspected it might be among Kempner's files.