Here is my situation: I have an MBP Retina 2013 with an SSD drive which I ran with Mavericks with no problems for about almost a year now. I recently upgraded to Yosemite which seemed to work well at first, but I found that it kept freezing up after an hour or two. This was unacceptable and I was unable to determine the cause so I decided to revert to Mavericks using my Time Machine backups, so I rebooted using cmd R. I selected Restore from Time Machine backup and followed the steps including unlocking the FileVault. It began to restore and then said it couldn't continue because of some sort of unspecified error.
So I tried to use the disk utility to erase the disk but the erase button was disabled. I did verify and repair on the Macintosh HD which did not report any errors.
Then I attempted to begin a reinstall OS X but that only sees the "Recovery HD", it doesn't see my main disk partition so I can't install.
Then I rebooted, hoping to simply boot back into Yosemite but it continues to boot to OS X Utilities no matter what I do. Now I try to do a Restore From Time Machine backup and its no longer able to find my Yosemite boot drive! I try selecting "Startup Disk" which doesn't find any startup disks. Somehow the main drive seems to be lost, I'm unable to erase it or even access it, what do I do?
Top drive partition ("Macintosh HD") does show under disk utility Partition: Name Macintosh HD, Format Mac OS Extended (journaled), Size 750.42 GB.
Edit: I've also tried booting to my DiskWarrior DVD but it just hangs on the Apple screen and never gets there! My next approach is to build a Mavericks USB bootable drive and see if I can install from there.
It seems clear that my main hard drive is locked or disabled somehow, I just don't know how to get it turned back on.