Sorry to hear. It was a long shot,but all I could think of.
CS5 does not have the autosave function CS6 has. You might want to upgrade to CS6.
If that's not within budget,here's a few third party autosave ideas. http://forums.adobe.com/thread/642893
Saving's not really a problem for me, since I ctrl+s every 5-10 mins or when I make a really important change.
I guess I have a similiar problem with this person:
but its really hard for me to believe the file's gone for good since I've been working on it for the past week...
I guess I'll consider upgrading :\
Consider getting an Uninterruptable Power Supply (UPS) before a new software package.
Did you make any backups of your saved data on a prior occasion? If not, consider setting up a regular backup. External hard drives are cheap.