Thats just absolute stupidity. They can't arrest you for what they can't find.
In my one instance? pure luck. focus was on weapons. They already found my m4 in plain sight, I also had my sks bullpup in the trunk, ready to go, along with bats, three foot long spike wrench, and a few other "weapons", I just got lucky with the drugs, I hadn't been smoking.
But for the most part, it is beyond retarded to have anything other than a blunt while you are smoking. If you get pulled over, eat it. Even if it reeks of weed, they can't arrest you for thinking they smelled weed. Eat it. I have eaten at least 50 blunts in my life time from seeing the black and blue in the rear view. Never regret it, I got pulled over on the way to the beach two months back. I smoked half the blunt with my girl, put it out, and about 5 minutes later, I got shot with the dar. 85 in a 55. Thats just my stupid fault, I have an addiction - called speeding. But not only did I have a blunt, I had an eighth in the trunk. The cop knew there was shit in the car, he asked over, and over, and over. I denied search because I was late for dinner, ate the blunt of coarse.
Its all about luck, but if you play it smart, luck can be on your side. Carry light, keep your car clean, be respectful.