How can police arrest you for transporting a controled substance if they never found any drugs on me

my friend was arrested and charged with 2 counts of transporting a controlled substance and has never been in any trouble before with the law and they never found any kind of drugs on her nor has she been in a vehical and been stoped and charged with any kind of drugs ..why is there still a case against them?

I doubt anybody can answer this question without knowing what evidence they're basing the charge on. If you know for sure that they have no evidence, the answer is that they can't unless you live in a hotbed of political corruption and your friend has really offended someone in power.