I was thinking about that.
Reminded me of the story of the African Union building being built by some China men and the AU only realizing later it was bugged.
Discussion
Supposedly three letter agencies used to offer secured rooms to foreign diplomats. The diplomats team would of course sweep the room right before the meeting.
The trick was, roll up copper screens in the walls. Sweep team comes in sees nothing because they are in a Faraday cage. Security leaves they roll up the screens and the room is now surrounded on three sides by every covert listening and recording device known to man 30 seconds later.