And I've seen past runs from a few groups that include that spot on thier ride. It TOTALLY looks like part of the trail. It isn't a bypass for something, it is WELL used, and there are no signs, or obvious shoe flys.
Unless you're misleading me with your description, and you may well be since this was your first time on the trail... That IS a part of "the" trail, but it is closed to motorized use. It has been signed in the past, and resigned. Someone keeps knocking the signs down, and you all know full well that just because the sign is gone doesn't mean it's suddenly open. You guys are not the first to go through there, either unknowingly or in total disregard.