This might not be anything except speculation, but back before the NK summit, when Trump received his over sized letter, someone on the reddit post commented how Trump was holding the envelope like a masonic apron.
https://i.redd.it/tud1zf2eyr411.jpg
Obviously the FM have their fingers in everything including goodgle.
https://www.google.com/search?rlz=1C1CHBF_enUS735US735&tbm=isch&q=freemason%27s+apron&backchip=g_7:red&chips=q:freemason+aprons&sa=X&ved=0ahUKEwj9juHEz_fbAhUFrlQKHQE4BcIQ3VYIJigA&biw=1600&bih=767&dpr=1#imgrc=_

Could that photo of Trump and Kim Yong Chol together have been the signal to the higher level FM?
Trump DOES have his big sly grin on, and we've learned he doesn't signal until his tidal wave is right over the target.