I recently reinstalled OSX, Win7 and Linux on my mid-2012 15" Retina (purchased August 19, 2012), and just noticed that I, apparently, am now running OSX Lion (10.7.5).
I recall that this machine came with Mountain Lion. I'm not sure exactly how this happened, but the only fix I have in mind at the moment is to do an internet recovery, which I hope will get the system back to ML; but, I'd rather not have to back up and restore 500+GB of Linux and Windows stuff in order to get a 4GB installer to download.
Suggestions?
Update
Forced internet recovery, which also says Lion instead of ML. Going to try nuking the recovery partition to see if that helps.
Best Answer
Depending on when you purchased it, it's possible that your machine came with OS X Lion preinstalled and you got the free upgrade to OS X Mountain Lion in July 2012. Apple's press release on the Mid-2012 MacBook Pro Retina dated June 11, 2012 states:
You can just visit the Mac App Store, sign in and install OS X Mountain Lion from there.