Folks get busted all the time shipping drugs through UPS. I've seen some crazy stuff, cocaine stuffed in a teddy bear. 10 pallets of cocaine with "for religious purposes" on the boxes. They deliver it and then they bust you.
They be busting people at the airport. I seen articles of people getting caught with cases of bottles of hot sauce filled with coke from the Caribbean, rugs with heron and opium in the threads from the middle East.
More times they know what's coming through and they let it go just to see who picks it up. Then they strike.