 How are people on Earth able to help with the search for a missing prospector?
Evans was a prospector, and like all prospectors, a sort of jackknife geologist, selenologist, rather. This was to allow the air-conditioning system to function properly, and to prevent air loss in case of the highly improbable meteor damage. For example, because of an order of his stating that there would be no alcoholic beverages within the survey building, the entire survey was assured of a constant supply of home-made, but passably good liquor. They claim that a radio that won't carry beyond the horizon isn't any good, and one that will bounce messages from Earth takes up too much room."
 They can see different sides of the moon from the people on the moon
 They can shine a light to make searching easier  Their equipment is advanced enough to connect to the prospector's radio  They can boost the signals of the scanners on the moon  They can see different sides of the moon from the people on the moon