The hierarchy manager could also have search functions.  For example, I have frequently seen functions similar to this:

std::list<GameObjects*> manager::FindAllObjects( predicate testFunction );
std::list<GameObjects*> manager::FindAllObjectsInRadius(float range);
std::list<GameObjects*> manager::FindAllObjectsOfType(objectType type);
std::list<GameObjects*> manager::FindAllObjectsOfTypeInRadius(objectType type, float range);

and so on.  The list of search functions tends to grow as the engine matures.

The hierarchy manager could also have search functions.  For example, I have frequently seen functions similar to this:

std::list<GameObjects*> manager::FindAllObjects();
std::list<GameObjects*> manager::FindAllObjectsInRadius(float range);
std::list<GameObjects*> manager::FindAllObjectsOfType(objectType type);
std::list<GameObjects*> manager::FindAllObjectsOfTypeInRadius(objectType type, float range);