The Facebook lawyers also accuse Ceglia of concealing or even destroying relevant documents, including six missing USB drives.

Ceglia could not be reached for comment.

Zeus Kerravala, an analyst with Yankee Group, noted that just because Facebook found one contract between Zuckerberg and Ceglia that had nothing to do with Facebook, that doesn't mean they didn't create another contract for different work. And that work could have been about Facebook.

"Who knows how many projects they worked on back then," Kerravala said. "The existence of this one doesn't mean a Facebook-specific one doesn't exist."

He added that the document doesn't help Facebook much, other than enabling the company to gain some favorable headlines in the news media about the case.