Then the corpse would have been located. A human body falling from a height doesn't drill into the ground. Also, the parachute would have been detected.
Reading that wiki summary it would seem likely that “Cooper” never made it out of the woods.
Speculation on my part regarding his lack of preparedness for the jump (no boots, poorly clothed, no steerable canopy) and the weather conditions (wet, cold, night) at the time could have resulted in possibly moderate to serious injury on landing in a remote area. Dragging himself to a water source, along with some/all money where he possibly died. Animals disperse the corpse, spring rains expanded the water source and carried money to where it was found.
