That it does. That lone speck on the firewall - is that a bolt? That flange has got to ground to something because it’s bolted into the plastic heater box. If it were me, I’d get any small gauge wire, put two ring terminals on each end, and run it from behind that bolt in the firewall to in between the closest screw in the blower flange and the flange itself. I’ve never seen a single wire blower motor without some kind of provision for grounding. Either that above or a second prong that a ground wire plugs into.