I'm sure he was speaking in terms of the main body of the sculpture being chiseled rather than built upon. This, however, may prove wrong in the years to come. I wonder, is it possible to frame and pour something the size and shape of the Sphinx -- given time, resources, unlimited manpower and knowledge...? The resulting concrete would be very similar to the stone from which the base was quarried.

Like as not, the rest of the limestone debris was possibly ground up for use as mortar in the chambers below the Sphinx and in surrounding structures that are now simply gone to time.

As for going, you and me both!

Cheers,
Dan