I hate to tell you this, but you are probably out of luck. We see this once a month or so, and people seldom manage to retrive anything worth while, but it is unusual to see this happen mid workflow. It usually seems to happen when saving, or is discovered when attempting to open a file.
You mave have something in the recovery folder if Photoshop consideres itself to have crashed, but I don't know what OS you are using. (Allways best to upload your entire screen at full res so people can more information).
You may be able to use one of the PSD recovery apps found on the Web, if your last save is also corrupted. I'm assume you save often? It is also a good idea to increment file names every 15 to 30 minutes in case of this sort of situation. A lesson the regular posters here have learned from other poster's misfortune.
Good luck, but my gut feeling is that you are probably not going to have any.