Verified answer

You could try and force-kill Excel from task manager, then run it again and see if there is an autosave version of your document available, but I wouldn't really count on that, since you saved the file normally and nothing crashed. It is most likely that you will have to code everything again. It's generally a good idea to pre-save every file you create in the desired format. To Excel's defense, you were prompted before saving the file and informed that saving in the .xlsx format will make you lose your VB project.