I always do backups, but this time I never had the need... Big mistake on my part. To my good luck, I made a usb installer 2 weeks ago to install MacOS Sierra on my brother's computer, I just need to go to his house and borrow his usb. I will follow your advice and make copies of every release of OS X that I have on the purchased section.
Thank You!
IMO, this is just another example of Apple making arbitrary changes to things for no real reason. This change makes no sense, it can no way be spun as an improvement.