Have you looked with a file browser rather than the gallery app? The possibilities seem to be that it's not really saving them or the gallery app isn't able to show files from where it is saving them. The latter would be possible if there was a .nomedia file in the folder it was saving to - which would be incredibly stupid, but could produce this result.
Can you still see images you had previously edited? If so that would seem to preclude the edited images being stored in the same directory.