In 1980, when I was a kindergarten student of the Qur'an, as I am now, I had the good fortune of hosting Dr Gary Miller at our home. He reminded me of the Mu'min of the century, Malik Faisal bin Abdul Aziz. We had also tried to arrange a lecture from him in West Palm Beach, FL but he politely declined to accept the assignment.
Before leaving for the UAE, Dr. Miller had strongly expressed his desire to live a very private life from then on but he declined to give any reasons. Probably, it was his failing health and displeasure with the Hadithi Muslims' undue pressures.
Personally, I do not know his whereabouts. I have just called and checked with a most well-informed scholar, Dr. Jamal Badawi, of Canada and even he knows nothing about the well-being and whereabouts of Dr. Miller (Abdul Ahad Omar).
You may hear Dr. Miller's speech on "Amazing Qur'an" at:
http://www.mydeviant.com/miller/gary_miller.html (Many speeches)