There is something about the story that makes me go "hmn" as far as just driving too far down one road and, Oops, you've crossed the border; seems there would be some kind of a checkpoint, at least. No matter the circumstances, they didn't have to be treated like they were hiding an arsenal of AK-47s in their intestines.
Why didn't they just NOT STOP, turn around and go back to Canada? The US police could not pursue them. DD