If your Mac crashes (never!) while you're in the middle of editing a document, it's possible to lose some of your data, especially if you weren't saving compulsively prior to the crash, and didn't have an "auto-save" type feature enabled. Programs like Microsoft Word and Excel (and some others) will try to automatically recover from these crashes, but sometimes they can't recover your data. Before you re-type all that lost work, here's one last thing to try.

Quit the program used to create the file you're trying to recover. Then open the "Terminal" program and enter the following command, followed by the "return" key:

open /tmp/`id -u`/TemporaryItems

This will open a folder that's usually hidden from the Finder, which contains temporary files that get generated periodically by various programs. Look for a file that contains part or all of your document name, or of the creating application name. Copy any such files to the desktop and try opening them (saying a little prayer to the venerated file recovery god can't hurt either).