The cable attaches to the heater valve that is mounted on the passenger's side inner fender. It sounds like maybe yours might be missing. One, or both heater houses would connect to this valve. I have seen it both ways and I'm not sure what valve is factory correct. Anyway, since the heater hoses have been bypassed, I wonder if this was just for as cleaner looking engine bay, or if the heater core under the dash had leaked?