This is a true story and happened last month. Kid had some drugs shipped to him. We have 2 drivers who deliver to his town and he stopped the first one that he saw to ask if he had his pkg. Driver said no but thought something didn't seem right so called the other driver to alert him. Sure enough, kid finds other driver but unfortunately for the kid the cops had found the other driver first and set up a sting. The driver delivered the pkg, got an autograph, and then the cops did their thing.
As far as the coffee grounds myth, we had the drug dogs come through and they alerted on a pkg. It was a bowling ball that had been drilled, stuffed w/pot, plugged, and then surrounded by coffee grounds. Same deal, cops set up a sting, driver delivered, got autograph, consignee arrested.
Obviously we can't catch all of the drugs that go through our system but we catch enough to act as a deterrent.