Sometimes these random full searches do happen.
I got one once traveling back to the States from Montreal. The agent said politely, "Sorry sir, but you have been randomly chosen for a full search. Please step over there."
Fortunately the full search meant a search of my bags and not my body cavities.
Funny thing was that I had bought a dozen or so Cuban cigars and, damn, I was sure that I was going to lose those. I had put them in a brown paper bag in a shoe.
The agent said, "Before I start, is there anything you might want to telll me about?"
I said, "Well you might find a bunch of my cigars in my shoes to your disliking."
"Anything else?" "Nope."
He searched my bags, found the brown paper bag, felt it from the outside to verify the contents, never opened the bag, smiled, and then told me to pack up and I was free to go.
Those cigars tasted pretty sweet.