The question is whether he said “No” when he was asked if the police could look through his car. If he ignorantly thought the police are always on the side of the good guys, he’s screwed.
If you know your rights, there are only two choices that you offer the police -
“am I under arrest, or am I free to go?”
If they ask to search the car, or where you’re going, or where you’ve been, or if you’ve had something to drink -
“am I under arrest, or am I free to go?”