From the original post in this thread, it seems to me you were the victim of poor communication by the organizer, poor pre event organization by the organizer, sloppy
sign in procedure, again by the organizer.
As posted above, it is the organizer choice as to who sits and who does not.
My advice, first take a class an become a CBJ. If you want to judge it is worth the time and effort. And second, patronize contests that have an organizer who actually organizes and communicates with his judges. If you do those things, I predict a happy judging future that will erase the sour taste you now have from an unfortunate and entirely preventible experience.
Carlyle, KCBS, CBJ, Organizer ( Judge Chair)