It sometimes happens to me that I have entered a lot of text in a text entry area on a web page, and then somehow I lose the page before submitting it to the server. Perhaps Safari crashes, I accidentally close that tab, etc. This "lost text" is often recoverable from the web browser's cache files.
For example, Safari keeps its cache files in various sub-folders of the ~/Library: Caches: Safari folder. If I recall some particular word or phrase from the text I lost, I can use the Unix grep command to search these folders for the cache file containing the text. For example, if I recall that the text contained the phrase random number then this command...
grep -r "random number" ~/Library/Caches/Safari
...will show which cache files contain that phrase.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051215063042481