Edo, in this case your gut was almost certainly wrong. Folks given rad materials are vastly more radioactive than their surroundings. Assuming they’re “fresh out of the oven”, they are 1000x or more “hotter” than the surroundings.
When I was working at Brookhaven National Labs, we had a shipment of medical isotopes delayed because the driver was “caught” by NY state police. (This was after 9-11). The cop’s gamma detector alarmed when the delivery man drove by.
In fact, this really isn’t uncommon. If someone’s had a medical radioisotope treatment, they will set off our local alarms. The only reason cops are seeing it now is because they didn’t have rad instruments until after 9-11.