I did not get that part- If somebody has received a letter, and somebody asks them 'Did you receive a letter?'
Are they supposed to lie or not initiating the discussion is good enough?
It is a classic variation on a dead-man switch. As long as one is able to deny receiving a secret order, one hasn't received it. If one is ever not able to deny it then the absence of a denial carries all the needed information with out violating the unconstitutional gag order.
A dead man's switch is a switch that is automatically operated if the human operator becomes incapacitated, such as through death, loss of consciousness or being bodily removed from control. Originally applied to switches on a vehicle or machine, it has since come to be used to describe other intangible uses like in computer software.
Developers of sovereign software would be wise to establish such methods of severing any temporary scaffolding tethers that connect them to their autonomous children so that they can passively disconnect from that position of trust should they ever become compromised without being coerced into becoming a source of malware themselves.
"Admiral, if we go by the book, hours could seem like days". -- Spock