The file may not be gone, but you may have lost links to the images.
To recover the file:
REMOVE THE PAGES "WRAPPER"
Press the [control] key and click on the hosed file.
Scroll to Get Info and select it
In the Name & Extenstion box, delete the ".pages" extension so that "myfilename.pages" reads "myfilename" and press [Enter].
Don't worry about the "will open in another application" warning. We'll put the extension back when we're done. Click [Okay] at the confirmation dialog.
The file is now displayed as what it is, a folder containing multiple files.
CORRECT THE PROBLEM
Next open the folder "myfilename" and browse to the index.xml file.
In my case, the offending issue was that the index file had been renamed to "index(xxxxx).xml.gz" by my syncing software. The icon identified the file as a gzip archive, so I simply edited the filename to read: "index.xml.gz" (without quotation marks).
Presuming the author of the previous post is correct and your file is no longer gzipped, you'll need to get a archive utility. Stuffit Standard has a 30-day free trial and is available at
http://www.stuffit.com/cgi-bin/stuffit_loginpage.cgi?standardmac
Other utilities, freeware, shareware and commercial, are available as well. Download one and Gzip the file and delete (or move) the unarchived "index.xml" file out of the "myfilename" folder. (Note that there are MANY different achive formats. I don't know if any will work other than the gzip that I found mine in.)
PUT THE FOLDER BACK IN THE "WRAPPER"
Back in the File Info dialog, click in the Name & Extenstion box, add the ".pages" extension after the last letter of "myfilename" so that it reads "myfilename.pages" and press [Enter].
Double-click you reconstructed Pages document. If you get a warning your only option at this point is to click [Continue]. At least you still have the text and layout. The only thing I've lost in the past is the images. You can relink them to their boxes.
Hope this works!
G4 800; Mac Mini Mac OS X (10.4)
G4 800 Mac OS X (10.3.9)