Downgrading from OS X 10.9.2 to 10.9
Yah, that's the problem with O/S X there IS no way to roll back O/S upgrades. On Windows you can do it but not on O/S X.

I have said it before but it bears repeating: clone your HD before an O/S upgrade so if it goes bad you can revert from your clone.

Yeah, I know, not what you wanted or needed, but I am not aware of Apple offering old O/S versions for download (though some clever web surfer might have found such). You may have to resort to (ahem...) "alternate" means of downloading earlier versions.

I would go that route, but clone your drive first (and TEST the clone: boot from it!), make a bootable installer thumb drive, boot from it and wipe the drive. Install the O/S clean and then use the Migration Assistant to get your personal files and Apps from the clone of your drive.

Not a lot of fun but unless someone knows a legit source (apple.com) for previous installers (unlikely) you'll have to go to that other "bay" and I don't mean "e."