The police in CA can't find out if you own firearms by running your license plate. They can, however, by running your license. The reason why LA's finest asked if the guy had a gun on board is because LAPD (and many other agencies) routinely ask that. What many officers will do is ask about guns, catching the driver off guard and if the person hesitates even for a second, they get the driver out and tear that car apart. Sometimes they ask permission, sometimes they don't. If they arrest you they will say in their report that you consented, whether you did or not. Most people are nervous and don't know that they can refuse.
A lot of non-CA people may find the original poster's incident surprising, but it's really not out of the ordinary. Growing up in southern CA it was very common to get pulled over by the LA County Sheriff for a minor traffic violation, and sat on the curb while your car was thoroughly searched, trunk and all. Then you got searched. Where are you going, where are you coming from. If you refused to sit on the curb you would be thrown on the damn curb.
LAPD has lowered their hiring standards going back 25 years and in the last 15 or so they've been hiring just about anybody. I know of people who flat out should never been hired, guys who kept getting turned down until LA hired them, sometimes applying even to LA a second time, and these cocky arrogant punks with badges are still out there...and those are the white guys. You should see the people hired through affirmative action including useless five-foot-tall females.
A friend on LAPD once heard his partner telling a prisoner who had boosted something from a clothing store "man, you should just grab an armful and rush the door like we used to do" or words to that effect.
One of the guys in the "Rampart scandal" had been detained and arrested five times for burglary and theft before he got hired. Another one couldn't get on anywhere because his background was so bad, but finally got on at LA. Just a bunch of goons with shaved heads.
There have been all kinds of gang bangers getting hired there--I could go on and on. I've heard old-timers, guys who retired 25 years ago, bitterly relate about how that department has changed.
A lot of cops think that everybody else shouldn't own firearms but these same guys are the ones who keep constantly spraying 15 rounds every time they get in a shooting...not only that but often they don't even hit the target.