I worked at BFS for 5 years and that should not happen, if it does it can have very serious consequences, and not just for staff.
Systems were put in place worldwide after the Lockerbie PanAm 747 incident and also 911, that should stop this from happening at all airports. I am not going to go into detail on a public forum. Despite these measures several major airports ( LHR and GAT ) in particular have this happening almost all the time. In theory airports breaching the regulations should be fined, or have their operating license suspended, but I don`t recall ever hearing of any.
Just in case anyone here was not aware, the Lockerbie bomb was in a cassette player in an unaccompanied piece of luggage.
A bag that does not have a passenger with it is triple x-rayed and opened and checked thoroughly, that`s the theory. Bags have been known to fall off trolleys being transported from the baggage bay to the aircraft, and other things can happen as well.
Off-loading passengers is no-fun usually for the ramp people, the bag or bags they need are often deep in the hold, and certain aircraft are more awkward to access and load than others.
The DC-9 / MD-83 was a real hateful thing to load/offload, and the 737-800`s are not much fun, some have a belt in the hold, which often jams, and if they don`t have a belt, it`s a long way to the back of the hold.