I quickly found the pasture which was supposed to contain the site.
Fortunately, Rick appeared after a short time. He told me the name of the owner, Mark McVye, and lead the way to Haigler where he hoped to meet Mark. After failing to find Mark there as well as on his ranch, his wife Karen enthusiastically allowed me to dig up EARTH after I had described the project to her.
She warned me of the rattle snakes that are often seen together with prairie dogs in their den and which announce their arrival with loud rattling.
I filled my bag with the EARTH from one of these dens.