I’m assuming a trackside drug test gives only a positive or negative result. Then a urine or blood test will determine what the substance is.
he has been taking painkillers for his injured shoulder. So if that’s on the ok list he is free to carry on.
if it’s a painkiller not on the allowed list I’d imagine it’s a short ban or fine
however if it’s a recreational drug he is in deep trouble. But we need to remember he is innocent until proven otherwise.