The anima® scene files are very small, so when you save a scene, anima® automatically saves a backup of that scene too, in the same folder.
The backup scene files have the same name but a different extension. The standard "ani" extension is replaced by a number sequence that starts at "001" and is increased on every file save, always keeping the lower number in the most recent one.
You can easily restore any older saved scene by manually renaming any backup file to a new name with the *.ani extension.