is this a secret or a bug?

[K_I_R_E_E_K]

ok, in the mission seek my master, or was it the from the depts, never mind, all i know is that in one of the ruins mission there is a room that on the map it shows a green rectangle (open door) but ot the cenerie it does not exist that door, only a fake door (it is a walll with the shape of a door) ok i know that there are hundrends of these doors along zones like caves, mines and ruins, but this one hapens to have a mark on the map.
is it a simle bug, or a secret door (i canot pass it tought)