If it's a door locked through a .pl, you will find that you can't open it with your GM flag on. I believe that is a known issue. However, I believe all of the Befallen doors are locked simply in the database as Trevius said.
There are a few different keys in Befallen, which door was it? This query will pull up the three locked doors in Befallen:
Code:
SELECT d.`id`, d.`doorid`, d.`zone`, d.`pos_y`, d.`pos_x`, d.`pos_z`, d.`lockpick`, d.`keyitem` FROM doors d WHERE zone = 'befallen' AND keyitem > 0;
I'd paste a handy little table like Trev did, but I've never been able to figure out how he and Cave make them look so pretty and easy to paste in =P