Had the same problem with my SUV. They do leave on occasion, I think by way of the windshield support channels above the fire wall in the engine compartment. I would place a packet of Decon there in a bait station when car is not in use and remove before driving. Then hope for the best. I would not use it if domestic animals or children are passengers in your car and you can’t safely control the area you place it. Also, continue with the traps in the garage.