Richie, get your mind and fingers where they belong. LOL
Lets say, they concentrate their efforts on the US. They could send the a letter, to each circuit. The only thing different would be how something was worded, or a change of location, or the color of the new release. They could pin down a location fairly fast.
Lets say, it is the color of the new book. Not that many colors to choose from. So some color choices would be doubled. The next letter, is sent to the circuits, with the right color. It would be an idea of what the next book title would be. Worded differently for each area. That would narrow the search more.
So now you have a circuit. Your mole is hiding somewhere in it. Divide it into fourths. Send letter to each, and you just narrowed it down to XX amount of congs. and so on. With letters, it wouldn't be that hard to find a mole.
Just really cultish though. But, we are dealing with lots of $$$$$