Comment # 3 on bug 852693 from Egbert Eich

Do you still see this issue on a later version than 13.1?

How did the logout happen? Did you get back to the display manager login
screen?
This indicates a crash of the Xserver, however the Xorg.0.log.old file did not
show any evidence of such a crash. Did you retrieve this file right after the
you were logged out and the login screen has appeared again?