If you think you've found it the first time, you're probably lost.
Road signs work on a backtracking system.
Seeing a sign probably means that you've just missed the turning. Different maps may mark the same spot differently. Maps are symbolic representations of territory that may or may not correspond with reality. Just because the policeman smiled at you and gave you detailed instrucions does not always mean he is right. The place you want to visit will be on the other side of the road.