I am surprised by the lack of searching. There are three possibilities, as far as I know.
1) there is a body somewhere outdoors which has not attracted any attention in the usual ways, and it was transported and left without being noticed. I understand the terrain; I live somewhere not unlike Tucson. But even so, I could not guarantee that I could do such a thing with no hikers, no side by side atv or dirtbike users, etc catching me at some point in the act or discovering this shortly thereafter.
2) there is a body in a structure somewhere which has attracted no attention. This is doable imo, as seen in other cases, but requires some luck or some very specific circumstances.
3) there is a living 84 year old woman somewhere with a substantial reward associated with noticing her, and no one has noticed.