This could have well happened (someone pretending to hear a message from God)
And keep for himself? Why not. And then write it down? Why not. And then what happen? "Abu Bakr"/"Utman" found the writings on the road? And inspired by the angel Gabriel they were convinced?
but not in the way Ibn Ishaq tells it
What way, any idea? I've personally none. The way Ibn Ishaq tells it is the only credible way for Arabs of this time. The Quran allows many narrative elaborations when heavily pressed.
and, anyway, the description of Mecca has nothing to do with Petra in terms of population and their respective religion.
Except the description of the map of Mecca in the 9th c. narrative as copied from the Petra one as shown Gibson : it is a remarkable and interesting point.
Well what makes his thesis irrealistic
Of course. Here we can see the great weakness of Gibson. If this guy has been graduated he would have never say what he says.
Petra is nowhere in jewish writings . Now Nabateans are supposed to come from Ismael's eldest son Nebayoth. Now is there any shrine for Nebayoth or for Ismael in Petra ? as far as I know, this isn't the case.
Of course all of this is bull***. The better is to stop talking about Petra = Mecca.
Procopius speak about the cave of the Patriarch in Hebron as a pilgrimmage place for arabs.
Do you have the reference?
There is one old article of Hawting about Mecca stuff : very interesting ... I did not know it as he does not post his work on academia.
http://www.bible.ca/islam/library/islam-quotes-juynboll-h