Hi Frank,
I think you made changes to the file and then saved, I advise you to use save incremental option while working so that you do not encounter the same problem in the future, in fact Cinema 4D does not save previous files except in the event of a crash, you will find a copy of the file by going to edit > preferences > open preferences folder and you will find the file in the burgerports folder, you could try that may find your file there for some reason, also if you modified the file and then deleted the original file for some reason you can recover the deleted file using one of the file recovery methods through the operation system (Mac or Windows), you will find topics about this on the net, I hope this is useful to you.