[ubuntu] 14.04: Glitch and crash during use, user data now missing

I was using my laptop to update some files on a remote server over FTP last night, and went to switch to another workspace when the screen suddenly "glitched" (best description I can give it; slightly corrupted visuals and unresponsive keyboard, trackpad etc), and the system hung for what seemed like 5 or 6 seconds. I was then kicked back to the login screen, where my useame was still listed along with the guest account and my password allowed me to log back in.

However, on logging in I noticed my wallpaper was missing and the default one was showing instead. All my user settings and dotfiles have disappeared, so apps behave as if they're being opened for the first time. All my photos and music files are gone, and the /home/ partition is showing far more free space than it should have available.

What can possibly have happened to cause the loss of all my personal data like this? Thankfully a lot of it is backed up elsewhere, but I've no idea how a seemingly simple crash appears to have removed user data without affecting the ability to log in to the account, or without the OS throwing errors.

Some general system info to help troubleshoot:

• Dell Precision M3800 ruing Ubuntu 14.04 LTS
• Intel Core i7, 16GB RAM, Intel HD & 2GB nVidia Quadro graphics
• Crucial MX100 512GB SSD with /home/ on a separate partition, and one user account (mine)
• System was under very light load at the time; Google Chrome with a couple of tabs open, Filezilla on a second workspace
• No other system instabilities in the year or so since last clean install