This isn't quite true. There are some X11 screen lockers (maybe only GNOME?) that coordinate with the login manager so that a crash just leads to a restarted login manager.

...but yes, most X11 screen lockers have this flaw.

anyway you can just skim through the altcrtl+Fn buttons untill you find the alternative screen root shell I left logged in.

fwiw TDE implements SAK. Don't know about anyone else.