“Admiral Rogers visited him and told him.”
That’s how I remember it as well, but I can’t find it right now. My bet is that Google doesn’t want us to see it.
Admiral Rogers was in charge of the NSA and his people had discovered and shut down access by an “outside contractor” that had been making “unmasking” requests.
Rogers went to candidate Trump and told him that his Trump Tower HQ was being surveilled. The next day Trump moved his HQ to one of his properties in New Jersey.
And the Fibbie who tried to enter Trump Tower with an unnumbered gun.