Today I tried to open a file and got the dreaded 'Unsupported Format'. After a quick Google search and a few less then helpful articles I found kind of solution.
I'm pretty sure corrupted files can't be recovered, but Manga Studio/Clip Studio Paint does keep multiple backups of recent files in your main Documents folder.
Windows 10 Example
C:\<User>\Documents\Smith Micro\Manga StudioData\DocumentBackup\
Replace <User> with whatever your main user folder is called. It's the folder that stores your My Documents folder, Desktop folder and all your personal settings.
Usually its under your C Drive, but I moved mine to my D drive ages ago, see image below.
I would recommend copying that latest file out to somewhere else and testing it in Manga Studio.