It does happen. A gentleman selects a suppressor at his licensed dealer and pays for it. The paperwork is filled out in the name of the man's properly created trust. The paperwork and $200 is sent to NFA Branch and the wait begins. The approved form comes back and the man comes to get his suppressor. He sees a fabulous pistol in the case and decides to buy it on the spot. A NICS check is run by the FFL because the pistol is not "covered" by the NFA approval. And the NICS check comes back as "denied"... And now the FFL has good reason to believe that the person is a prohibited person and refuses to complete either transaction. Guess how upset folks are?