Some maps, in particular military maps, use a coordinate system other than the familiar lat/long system. One is called the UTM grid, and it is rectangular grid that makes it easier to measure distances on a map than lat/long. It was pretty clear that the coordinates you found couldn't be a complete description because only four digits does not give enough accuracy to pinpoint a spot. I figured that they were just using the last four digits of a standard grid of some kind. When I tried using the numbers as the last four digits of a decimal lat/long description it didn't work because the points were not in the area where we are looking. Geographical locations in one rectangle of the UTM grid in our search area is described as 15S 29****E 387****N where the asterisks could be many different numbers. All of the numbers could change with position, but for small changes in distance only the last four numbers would change. I believe that the searchers were using only the last four digits as kind of a shorthand notation because the other numbers were known and would not change within the area they were searching. The searchers described the location of clue C7 as 9843/7565, and I believe that the actual complete UTM description is 15S 299843E 3877565N. This point on the surface of the earth can also be described latitude 35.020940 North, Longitude 95.193840 West, or commonly 35.020940, -95.193840. I just made the conversions for all of the clues in the post because most people use lat/long descriptions with Google Earth.
On my topo these points are clustered together a little over a mile north of the truck and a little less than a half mile to the east and they are not far from a road. If you believe that my guess as to the meaning of the numbers is incorrect, please let me know and I'll think some more on it.
