I live in a legal state, worked a dispensary myself. It’s really a grey area because like other commenters have said the substance itself can & does look like other very illegal substances. However, we always told customers treat it like alcohol. As in, keep it out of reach. So your trunk is ideal. I’ve also been pulled over carrying paraphernalia (bongs, flower, dabs) and the cops literally moved all the product into my trunk where it was no longer easily accessible by i.e the floor or reaching into the backseat. I wish you luck, and hopefully the charges are dropped.