I'm missing last one too , but I'm not that eager to look for it > I'll crash it sooner or later :D
I have followed 3 or 4 different maps and videos, and the same one is missing in game. It's near a FORD on a building site not too far from a gas station. I remember getting it before my game crashed and I lost a save (pre that massive patch to add the new DLCs). Since the massive patch the gate has gone - I even uninstalled the game and deleted all saves. I will try tomorrow to uninstall and NOT download the patch when I reinstall. (I am on PS3.)
