Where the files went in Mavericks
This has been a useful thread for me.
OK: just for anyone else.. and if you do have Time Machine.. This did require time machine, and worked on OS X 10.9. It may work on 10.8 too.
I closed a doc which was untitled and unsaved, which my wife had spent an hour working on. The modern dialogue box actually makes you click "delete". Oh dear.
I hoped that a recovery file was on the HD from before. It took a bit of digging. and this thread here talks about various locations where the files end up... so that if you can go back in time you will see them.
It did not work for me On OS X 10.9, Pages 09 and 5.0.1 (the latest). In the end I opened up a new doc on a different mac, to see where the Untitled temp file ended up. It seemed to turn up in Finder search on iCloud. A bit more research here: The temporary files get saved to ~/Library/Mobile Documents/com~apple~Pages, where the first "~" is the user's home folder. To get there from the finder, hold the option key down and click on the "Go" menu. The Library folder will be in the list (it won't be if you don't hold down the option key).
Navigate into the folder, and then activate time machine, and go back to the time you last remember working on the doc. If you see multiple "Untitled" documents then select each one and tap the space bar to see the contents in preview (even whilst in time machine). Then Bingo.
The tip works for Keynote and Numbers too... Under the respective ~/Library/Mobile Documents/com~apple~Keynote and ~/Library/Mobile Documents/com~apple~Numbers folders. HTH.