I see nothing at all illogical in what you describe, when one realizes that those who searched for the mine, were mixing together information from several different mines located in the same general area, in the belief that they must all be the same mine. It is not like there were giant billboards put up to mark the way after all, and the two closest to Waltz clearly did not pay attention to what he was trying to tell them.
"Reiney you better listen!
That mine is hard to find, even when you know where it is!" --Jacob Waltz
"You will wish you had listened better when I am gone." --Jacob Waltz
Waltz seems to have had a monumented trail that would lead to the mine, which unfortunately many monuments have been destroyed, altered, and fake ones put in the Superstitions so any hope of trying to follow that trail of stone monuments is now gone.
Whole cities have remained lost for centuries, millennia even, so a small gold mine, that the owner had concealed, located in a remote wilderness area, is not hard to understand why it has not been found. Then too 200+ people all claim to have found it in 200 different places. They are finding something, which can not be done if one decides it is all a fiction and stays home.