Will a drug dog smell weed on a backpack just from it being in the car with weed?

[Dylan Lancey]

I keep 2 backpacks in my car; one that I keep weed and paraphernalia in (the bag smells like weed from the outside also) , and my regular school backpack. My school does random drug searches in the classrooms where they tell everyone to leave there bag and exit the room so that the dogs can smell. I have smoked in my car, and the backpack with weed and all of my other stuff has been all over the car, because I don't always put it in the same place. If my school backpack as been in the car or on a spot where the weed backpack has been, will a dog be able to detect that and respond to it as bad? If so how do I keep it from happening from now on?