Seems easy to find you way in open terrain or in a city where the sites are familiar. In open terrain there are all the natural direction indicators that we have instinctually used for aeons. In a city where sites are familiar there are the patterns that we have come to recognize. Some of these are recognizeable even from unknown neighborhoods such as the skyline.

In a city in panic with the skyline damaged or obscured by - pick your event ( Storm: Quake: Terrorism) and people behaving - pick your modifier (panic: riot: dazed and confused:) most of the landmarks that you subconsciously recognize and navigate by can't be counted on and the paths you are used to using may not be passable / safe. Similar problems arise in more rural areas though the natural direction indicators are less vulnerable to some of these events. The sun still rises in the east and if that stops happening then we won't be here to witness it.