Old school way with a map and compass and a pencil. Find three known locations, shoot an azimuth with your compass to them, convert magnetic north to grid north, draw a back azimuth on your map from those 3 locations, where those lines intersect that is your location. Shoot another azimuth to where you think the animal went down, convert magnetic to grid north again, plot the 180 azimuth on your map to your location, then go get it. Or I'm sure one of those newfangled GPS units will do the same thing. Or make a mental note of where it went down, walk over to the spot and if it's not there lay down a marker of some sorts on the ground then walk in a circular pattern til you find it.