I have never had this happen with vc++ before but sometimes when running an app not as administrator files it saves will not really be saved to the folder which it says they are being saved to. They are instead being saved someware in appdata. Also, you will see the file from a open file window run by the app, but you will not see it if you browse to the folder or if you try to open it as administator.
So, try running vc++ not as admin and looking for the file.
You can also search for the file in appdata. This is usually in the user folder, but it may not be visible.
You can also try searching your whole c drive, and searching your Recycle Bin for the file.
I'll get a new signature someday.