A similar thing happened to my wife (then girlfriend) and I at the Canadian border. She admitted to having mace. They made us pull over and I really had to use the restroom. There was a sign indicating a restroom right there, so I got out to go, but they motioned me inside and searched everything in my pockets and the linings of my clothes and my girlfriend's clothes. They searched our vehicle and all our luggage. Didn't go as far as to use fiber optics or remove door panels, but it was a very thorough search. Finally, they let me go to the bathroom and let us go after signing some paper saying that she "relinquishes her mace to the crown" or something. We haven't been back since.