Worked on the 2nd try for me, daytime. The body wasn't there the first time, but when I went away and came back, a corpse in a green coat was just inside the cave entrance. Carry him to the bone pile, and out pops the bear.
And do not sell the skins to the peddler!! He rips you off big time. Send them by naval convoy to Saint-Augustine. Naval convoy gets you $1500+ per skin, the peddler gives you $240.
If you upgrade the convoy capacity to max, you can get $23000 or more per trip.
Ya I quit and reloaded my game and the body was finally there.