If you didn't smoke, you're okay. Don't drink to much water, it can make you sick and throw off you're balance of your urine (gravity, creatine and ph levels). Then the test people would be witching about you trying to dillute something. Unless your uncle rolled up the windows and it was so smoky inside the truck/car he couldn't see the road (basically getting baked out), then i wouldn't worry. But he rolled down a window and most went out with it. Just because you "smell" weed doesn't mean you inhaled it.