Well, that was embarrassing. Archivists recently found the 1903 Wright Brothers patent for their airplane, after it had been missing for 36 years.

“A sleuthing archivist found the file March 22 in a special records storage cave in Lenexa, Kan., where it was sent at some point after it vanished around 1980,” writes Michael E. Ruane in the Washington Post. It should have been stored in a “treasure” vault with other priceless documents in the National Archives and Records Administration (NARA) building in Washington, but when officials preparing for a commemoration looked for it there in 2000, it was gone, he writes.

Yes, it was literally in a cave. The cave records center opened in 2003, and the NARA patent files were sent there some years later, Ruane writes. Among 15-foot-high stacks of boxes, the precious file was eventually found.

There’s been a lot of interest in the Wright Brothers since the centennial of their first flight, in 2003. David McCullough published a book, The Wright Brothers, a year ago, Tom Hanks is producing for HBO a miniseries based on the book, and Steven Spielberg has reportedly expressed interest in a film. So the discovery came at an opportune time.

Well, maybe not as opportune as finding it in 2000, when they first looked for it, likely for the 2003 centennial. To make up for the omission, the NARA is holding a special exhibition of the patent starting in May to celebrate the 110th anniversary of its issuance.

“But how did such a treasured record wind up in a storage cave 1,000 miles from Washington?” Ruane writes. Most likely through a simple filing mistake decades ago, according to NARA Chief Operating Officer William J. Bosanko. “Unfortunately, with billions of pieces of paper, things sometimes go where they shouldn’t be,” he told Ruane. “If somebody puts something back in the wrong place, it’s essentially lost.”

“With more than 107,600 cubic feet (3,047 cubic meters) of patent files in storage at the National Archives, containing 269 million pages, it’s not very difficult to imagine how a single patent could ‘disappear’ if it were mistakenly filed in the wrong spot,” writes Mindy Weisberger in LiveScience.

The Wright Brothers patent isn’t the only significant historical document that’s gone missing for long periods. During a digitization project, the NARA recently discovered a letter written by poet Walt Whitman on behalf of a dying Civil War soldier, about ten years after he’d written his seminal Leaves of Grass in 1855. Further afield, researchers recently found a new copy of Shakespeare’s First Folio in a Scottish library. And copies of the Magna Carta are still turning up after 700 years.

And those are the historical documents that have been found. How many historical documents have been misplaced, while the poor sap who was supposed to be in charge of them silently hopes nobody asks about them? (Can you imagine being the guy in 2000 who had to admit they couldn’t find the Wright Brothers patent?)

As it turns out, there’s so many missing documents and artifacts that NARA has an entire program, the Archival Recovery Program, which hunts for them, Ruane writes. In fact, it just added two extra archivists to the program in February. “A perusal of the Missing Historical Documents and Items list, which the Archive maintains, includes several types of documents such as a collection of telegrams penned by President Lincoln, a collection of presidential pardons also dated to the nineteenth century, and the patent drawing that accompanied the application for Eli Whitney’s invention, the cotton gin,” writes David DuMar in NewHistorian.

It also goes to show that if it’s that easy to lose an important historical document, how easy it is to lose something less important and less historical. And even if it’s not historically significant, it could still be important to you. That 2013 invoice may not be going into a museum, but it’s still going to come in handy at tax time, when the company is audited, or during electronic discovery for a civil case. Proper records management means keeping records safe and accessible, as well as tracking important information about them.

We suppose we can’t really blame the Wright Brothers, though, for not having scanned their patent application. Maybe if they’d lived long enough, they’d have invented the scanner, too.