If you are using windows 7 or later, you can try opening the folder in windows explorer, right click on the CDR, go to properties and then the previous versions tab. It may have kept an older version.
I can't remember if XP also kept previous versions and it also depends on your configuration, so it is not definite that you will have them.
Another, small, possibility is to look in the same folder and see if you have a file which begins backup_of_... and your filename. But this keeps only one previous copy so if you have saved the file more than once since Wednesday your backup will be too new.