When I started working decades ago, we were taught how to use bent bits of fence wire to find underground pipes before digging

I literally found scores of pipes that way, and saw dozens of other people do it regularly. It was even taught at a local agricultural college as part of the horticulture course

Then someone told me it was a myth and doesn't work, so I set up a blind test with a hidden bucket of water and I utterly failed to find it

I simply cannot explain this