You have a very good point; it just happens that the two occasions where I used a compass on land were during nights with extensive cloud cover. Dawn will come however, and East will be revealed. Don't forget that compasses can be fooled (iron on your body etc., local variation).

It is important, if using a topo map, to use it to track your progress and stay found - don't wait until you are confused. Even GPS units can be a little off in steep canyons; nothing is perfect.