I was going through the same thing for a few weeks, then logged in to my FAA Drone Zone (FAA DroneZone) account and found the FAA posted their letter there and gave their reasoning. Give it a try; you should find your notice from the FAA there.
Agree with Jesse G above that all the info is available online. The best place to start is www.faa.gov/usa; all the material is available here for free, even the Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25B) in PDF. I gotta admit, I'm not the best at cracking a book, or PDF...
Hi all, happy to join the new Commercial Drone Pilots forum. I'm currently flying a DJI Phantom 4, a Phantom 2 and a Yuneec Typhoon H. I have had the FAA's Remote Pilot Cert for a year. I also train others to fly. Again, good to be here. Cheers.