Something kind of similar happened to me years back! Me and my OH had been out clubbing and stupidly accepted a lift home from a friend of a friend who we knew was a bit dodgy but it was a whole lot easier than waiting for a taxi. Anyway we were nearly home when he got pulled over. The police got us all out of the car and then searched the car and lo and behold there was a stash of drugs in it. We all denied it was ours (obviously only we were telling the truth) but they arrested us all and we spent what was left of the night in a cell, great experience not! We both got interviewed but they hd nothing on us as we hadnt done anything so were free to go. The driver did get charged with possession and intent to supply.