Just curious...in the shifting sands of the desert over thousands of years, what evidence would there be of anything? Along the same lines, they brought up a *WWII airplane in Greenland that had been under 268 feet of snow and ice--if they hadn't known what we were looking for & where, would it have been found? Nature moves things.
*http://www.greeningearthsociety.org/Articles/1999/squadron.htm
It's hard to do archeology in wet, moist soil when they used mud bricks and part of the delta was destroyed in floods and tidal waves. Think New Orleans and Katrina.