In broad daylight on Sept. 11, 2003, somebody deposited what could have been a "dirty bomb" at the Washington Monument. U.S. Park Police never noticed. It wasn't a real bomb, just a suspicious-looking black plastic bag stuffed with garbage. And the culprits weren't terrorists, but investigators from the Interior Department's Office of Inspector General, out to demonstrate the monument's vulnerability on that infamous anniversary. As documented in photos and a memo obtained by The Reliable Source, the feds left the bag at the rear of the obelisk for 20 minutes, then moved it near a security checkpoint where tourists lined...