Despite what the law says, it really depends on the area you live in. In the nearby small town that I grew up in, I spent an hour on the side of the road while my car got searched - my CHP was "probable cause" that I had a gun in the car.
Well, I don't have all the facts on this, so I won't try to justify or condemn what the officer in this case did, but the presence of a weapon (legal or otherwise) or other indicators that a weapon may be present (such as ammunition, magazines, etc.) can justify a "vehicle frisk" for weapons. It is not a probable cause standard, but a reasonable suspicion standard. The courts have upheld "vehicle frisks" for weapons based on reasonable suspicion are OK, so long as only places where I weapon could be located are searched. For example, an officer could look under seats, in the glove box, in bags and boxes in the passenger compartment, etc., but it would be much harder to justify opening a film canister or ring box. Any evidence discovered during a "vehicle frisk" is admissible, and could result in probable cause to conduct a complete search, which would include the whole vehicle, not just the passenger compartment.
As a practical matter though, I'm not sure what the point is of doing a "vehicle frisk" on a CHP holder would be. Lets say I decide to do one based on the presence of handgun ammunition in plain view. I discover a handgun in the glove box. Since the driver has a CHP, I still don't have a crime. I've never done a "vehicle frisk" on a CHP holder and I can't see a time when I would. I'm not even sure that I would consider simply having a CHP to be reasonable suspicion that a weapon was present. On the other hand, I have a CHP myself, and I always carry a gun. All my friends who have CHPs (and are not LE officers) also carry guns 90+% of the time. I think I could argue, based on my training and experience, that CHP holders are often armed. So it probably does amount to reasonable suspicion, and I suspect that most courts in NC would agree.
All that said, I'm not sure I like the precedent that sets, and therefore I'm not going to be doing any "vehicle frisks" based on a person having a CHP. Still, folks should be aware that such a frisk is probably perfectly legal and consider that when dealing with officers, some of whom (though in NC thankfully not most) are going to be anti-gun.