In the article, he says:

"Through a friend of the family who used to work for the FBI, I later learned that as soon as I had left the Customs interrogation room, the local FBI office in Savannah, Georgia (where I was headed to visit my mom) had been notified of my arrival. As a result, the FBI then tapped the home phone at my mom’s house."

So it sounds as though it was through this same "friend" he learned of the phone tap as well.