Many years back I remember seeing a story on the news about a similar incident. It seems a small bear was stuck up a tree and they sent the sheriff out, who brought animal control out, and then the local TV news crews were out there too. They darted the bear, but he didn't budge (though he still seemed to be moving around up there. Then they darted him a second time, still no results. Then they got one of the sheriff's deputies to climb up the tree a ways to get a better look and maybe see if he could be shaken off the branch.
It was a black trash bag.