Help! - Course Unit Pages Disappeared

Today, I was adding information to a page within a course unit. There were 7 pages, 5 of which already had content. I had just copied and pasted content into one of the text fields on page 6 and pressed <Save>.

The page refreshed, and ALL of the pages were gone. There was the 1 default page, with only the title that I had originally created.

I logged out, logged back in, deleted cookies in my web browser. It's still gone. The database must still be intact, because all of the comments and discussions added today are still there.

Please help! The 5 pages that disappeared represent about 6 hours work, and I really, really, really don't want to have to recreate it. Any ideas about where the data went and how I can retrieve it?