When you have a document that is ABSOLUTELY CRITICAL and undergoing RAPID CHANGE...

Make frequent backups, even if it is 236MB.

Because when you're system spontaneously reboots in the middle of saving a change to said document two days before the big presentation where you need it, there's a good chance you won't get it back.

Fortunately for me, I was quite lucky and was able to repair the file in question -- a presentation produced using Apple's Keynote package. In this case the main copy of the gzipped XML that represents the actual content of the document was gone, but a temporary version was entirely undamaged. And since Keynote uses "bundles" (a MacOS construct where a directory looks acts and tastes like a single file from the GUI -- but is still treated as a directory from the shell), all I had to was go in and rename index-temp.apxl.gz to index.apxl.gz, and I was good to go.

Had it been worse, I would have lost a very substantial amount of editing and new content that I had not yet pushed to an off-site location.

*phew*

-JF