I have been searching and trying to correct my mid 2011 MacBook Air screen when you startup by holding the option key. My Bootcamp no longer shows but the created USB Windows 10 install stick does even though it is not connected.
I have Yosemite, latest version, and Parallels 10, latest version. I have imported my Bootcamp as VM and it works perfectly in Parallels and it used to work as a startup OS.
Since I usually use Parallels to access my Windows install I am not sure when it quit working.
The Windows install stick has been living on the option start screen since my son made it and we used it to install Windows 10 back in August.
Another recent find was my recovery partition, which showed, but failed to boot. I was able to access Internet Recovery but it only wanted to install Lion, strange. I managed to fix that by target disc mode with my MacBook Pro and reinstalling Yosemite, but still have the Bootcamp issue and the USB stick "ghost."