@matigo Wow. Just checked the App store. Everything from Lion up to El Capitan is still there. No Sierra.
Good thing I found out about this before tomorrow night since I was going to totally wip and restore it. (I may have Sierra on a external drive from where it was downloaded though. I'll have to check)
If I have the installer still, @indigo, I'll PM you a dropbox link so you can download it if you like. (It will be a while though as I am a long way from home)