the cameras are looking. and they're getting better with time.
more than once i've had an attendant come over (from a different area, out of sight range) check my bags, cart, and screen because they were notified of a possible 'mis-scan'. by who? i dunno if it was automated or from LP.
and it's always been for some cheap little shit like a tub of sour cream or can of veggies or something. never 'found' anything, though.