Paul Ceglia, the man who last year claimed he owned 84 percent of Facebook, has been ordered to return to the U.S. to unearth the one piece of physical evidence that could settle the court case.

Ceglia, who is currently staying in Ireland, was ordered by U. S. Magistrate Judge Leslie G. Foschio to return home to the States to search for one of six flash drives that Facebook says will settle the case in Facebook’s favor.

Ceglia said the drive was lost; however, given that billions of dollars and ownership of the world’s most significant social network are at stake, the court won’t simply take his word for it. He has until December 2, 2011, to find as many of the six flash drives sought by the court as he can.

So far, Facebook has gotten everything they’ve asked for in this case, as sources close to the matter tell us, on both privilege claims and discovery.

In July 2010, Ceglia had Facebook CEO Mark Zuckerberg served with papers. Ceglia said that he and Zuckerberg had entered into a contract nine months before Facebook launched. The contract allegedly stated that Zuckerberg would “develop and design a website” and that Ceglia would wind up “paying a $1,000 fee but getting a 50 percent stake in the product.”

At the time, Facebook dismissed the claims, and Ceglia had few supporters among the tech-blog-reading public.

But Ceglia persisted. In April 2011, he came back with an impressive law firm, DLA Piper, at his back and some new evidence.

Ceglia produced emails (which Facebook claims are forgeries) showing Zuckerberg attempting to swindle Ceglia out of his share of the company. The emails were allegedly written during the same time period Zuckerberg was stalling his work for the Winklevoss twins.

Given the fact that Facebook reached a $65 settlement with the Winklevoss twins, we can’t really say whether the company is willing to bend on this claim, either.

What we do know is, according to court documents, Facebook asked the judge in the case to order Ceglia to “conduct a diligent search” for the missing flash drive in the United States. He will also have to give details about “the dates, times, locations and circumstances of his in-person, good-faith efforts” to find the missing drives.

Also in Facebook’s favor, the company will be permitted to issue subpoenas to various people involved in the case. Facebook will also be allowed to examine metadata from experts’ files.