'Undo' function, undoes 'Save'

I’ve just lost some work. Scapple went a bit funny when I was moving a ‘Note’. I placed it over another ‘Note’, which didn’t render properly. So I used the ‘Undo’ function, hoping to start again. Went back too far, went forward, using ‘Redo’, went back again, then tried to go forward, but was unable to. I thought that because I had used ‘Save’ each time I wrote a ‘Note’, that this would save the file, at that point. But it seems that the ‘Undo’ function, undoes ‘Save’.
I’ve looked in various locations (AppData/Temp, etc) for previous versions of the file, no luck. The ‘Previous Versions’ facility of the OS (Win 7) found one version of the file, but not all work has been recovered, the version was from twelve hours ago.
Is there anything else I can do?
Thank you.