By the way, in the same mine, there is another hidden room where you can save a girl who is their sex slave. You just have to pass a narrow passage behind the mine cart/trolley. Another way to find the room, if you are not doing a virgin run, you can basically lose the battle with an orc, and you spawn in that prison room, and after getting three days gang banged, you can pick up your weapon and cloth, and run away with her.
beside the aforementioned rooms, There are few hidden rooms through out the maps, that are very well hidden, and the passage to those rooms appears only when you press yourself against the wall. There are chests in those rooms, that contain some legendary items/weapons. If I remember correctly, there should be two such passage in orc mine. One almost at the beginning, and another at the end of orc mine.