BryanP, one carefully monitored anything is pretty much irrelevant to anything. Why it works or doesn't work in any one and only one given situation just doesn't matter.
Dowsing is known to work for some people, some times. Not everybody, certainly, and not all the time for those who have had success.
I'd consider it a fair test if a dowser could go out into an area where most drilling efforts have been to no avail, and find water where others could not. (Assuming there is actually some sort of groundwater formation in the vicinity) If he says, "Drill here." and sure enough, they hit water, that's as controlled and monitored as ever one could wish. Results are what count, not the number of witnesses to the dowsing effort.
That's why I brought up the Marfa Lights. Folks have been studying and theorizing about them for over a hundred years. Some things, I guess, are just forever gonna be part of the Great Unknown.
, Art