You may be right, because, unfortunately, that is often the way law enforcement works--bring as many charges as possible against people who are unlikely to have capable legal advice in the hope of getting a plea on the most important/legitimate charges.
But--as Olympic Fan has pointed out, it's apparently not illegal to own an unregistered gun in NC, so unless the police could not only connect the gun to the people in the car (which a clip might do) but connect it to something illegal--having been stolen or having been used in a crime, for example--it might not make any difference. Although I don't remember seeing any formal report, I think I read somewhere (maybe on Pack Pride?) that the police determined the gun was "clean."
Granted, as Urinal Cake noted, the presence of a gun does suggest the possibility that the people in the car may have been dealing rather than just possessing, but I doubt that kind of inference, without more, could be the basis for a criminal charge. For what it's worth, my gut instinct (also, clearly, not relevant in any legal proceedings) tells me that they were not actually dealing, gun or no gun.