All may not be lost! Give www.cgsecurity.org/wiki/PhotoR… a try. I've only ever had to use it for text documents myself, but one of my friends managed to successfully recover a completely corrupted .psd file using PhotoRec. The interface can be a bit weird if you've never used the command line instead of a graphical interface, but there's a handy walk-through on the wiki.

You will want to narrow the search parameters down to just Photoshop files, because it will find absolutely everything. If all goes well, it's possible-- even likely -- that you will end up with multiple copies of the corrupted files, each one from a different save point, and will have to do some digging to find the most recent version.