So rather than poking many holes in the ground probing for the tile, I would locate the tile within a foot. That summer, I worked with different teams of surveyors on many farms in the county. I would always witch for the tile and always locate it. Now, I realize that this should have been impossible and maybe it was. But, I was there and did that.
People stick holes in the ground and find what they are looking for all the time.
I've even seen it done myself. I've thought of trying it again, maybe when the snow departs the Midwest I go out in the country and again try it. Although, now I know it can't work. You'd be looked upon just like those pranksters who make designs in wheat fields. As a natural born skeptic myself I usually set out with the purpose of debunking claims that don't seem plausible.