While doing a clean install, which I've done dozens of times, the main HD was deleted. It doesn't show up anywhere. I had the "Install Yosemite USB" inside. So the OS got installed in the USB. Now, I can not find my main HD, boot from it or anything. When I restart the computer and hold alt or command+R NOTHING happens, just a black screen. I have a 2013 11" i5 MBA. Any help would be appreciated. When I am in Yosemite and go to Disk Utility, the only disk that shows up is the USB where the OS is installed.