Down the side of the passenger seat i bet, or even by this time under the seat itself..... as long as the door was shut when you took out the blood test kit, chances are it would of slid sideways and rolled.... or potentially if you had a bag on the floor of the passenger side, could of fallen in there.... either way, if you don't find it, if you ever sell the car, you'll have to leave a note explaining what it is to whoever finds it![]()