The Trump people knew this. That why the Russia lady said Manaford never looked up from his phone the whole meeting on GMA...
I thought I was nuts for speculating this very thing last year after Election Day.
I've had this suspicion that Trump's people were onto some kind of electronic surveillance of their campaign, and they used it to their advantage in the election.
It sounds outlandish, but it might explain two things that always seemed odd to me:
1. Trump's victories in Pennsylvania, Michigan and Wisconsin (I can imagine a bunch of staged phone calls and e-mail communications among senior campaign staffers wondering why they were spending so much time in states that they knew Trump was going to lose)
2. Rudy Giuliani's disappearance from public view soon after the election (his security firm probably had the Trump Organization as a client for some time and would likely have been involved in cybersecurity efforts for the campaign, which would have made him ineligible to serve in any cabinet role with the new administration)