They never found the money, either
Part of the money was found: https://en.wikipedia.org/wiki/D._B._Cooper#Recovered_ransom_money
But most of them were never used, they documented the serials of the bills.
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.
My theory: the parachute they gave him was packed to not open. He’s impacted several feet into the ground somewhere.
He asked for four, two main and two backup. Of those one backup was non-functioning and the other was supposedly possibly by him to carry the money.
He asked for two sets specifically to imply a hostage might be jumping with him, to negate the option of parachute tampering.
I thought I saw in a documentary that it was proven to be Loki after losing a bet with Thor.
There was another documentary that says he fought Bigfoot while a bunch of shirtless guys went jogging.
