Unfortunately I can't go back.
There's still something wrong in that under normal circumstances when a unit is eliminated or runs off the map, the Next function skips over it and the unit menu shows its status. In this case Next goes to it and the status is Ready. It looks like the location was changed to -1,-1 but nothing else was.
I'll go to flip-flopping save files so I'll always have the previous one available if something strange happens.