I don't see how an organization like the WT would let somethign like this slip through their fingers and not document it somehow."
Because the pinnacle of the Society is also part of the network of these "secret societies" and they are well aware of how these things work.
Assignments that risk your reputation are given not only as initiation but also as punishments. Sometimes these type signals are even used publically to send confirmations of allegiances.
I am sure the society was well aware of it at some level. They could not make use of it because it would jeopardize Jeopardy!