My MBP froze as I was typing a final paper, so I proceeded to force restart (holding down the power button). Ever since, I've been getting the flashing folder and question mark on startup. I've tried booting in Internet Recovery Mode and Single User Mode. Macintosh HD is not showing in Disk Utility and diskutil list does not return any core storage volumes in Terminal. I've tried reinstalling my OS X from an external recovery HD (flash drive) but when I get to the screen to select the disk on which to install Mavericks, my Recovery HD is locked. Running fsck, I found there was an error on my Recovery HD but that was repaired and I rebooted. I've also reset NVRAM with Command+Option+P+R. 2013 MBP 13" w/ OS X Mountain Lion preinstalled; upgraded to Mavericks. Unfortunately, I just came out of warranty, and I find it hard to accept that my 14 month old hard drive is irreparable. All help is greatly appreciated!