I have often thought that such equipment would have had to belong to someone besides those living on Earth for it to disappear so cleanly.
Just speculating here, but in answer to this, and your previous post, I'd have to agree that much of the machinery required to build those monuments must have left the area with those who built and owned it.
It seems likely to me, that the parent group of beings spent some length of time raising up the local stone age people to a civilized state. During that time, they would have used their technological prowess and equipment to build lasting artifacts, which may have even served other, unknown purposes, at the time.
Perhaps some of the more intelligent ancients were instructed in the use of some of this advanced equipment. Perhaps some of it was left behind when the parent beings moved on. Over eons, even the best steel machinery will succumb to the elements, and rust away to dust.
Then again, the parent group may have taken everything with them, leaving only memories of how the 'gods' invoked 'magic powers' to move heaven and earth.
It's also my belief that egyptologists have squirreled away found evidence that does not comport with the prevailing paradigm of Egyptian history. Unfortunately for them, much of the best evidence is right there in the stone for anyone to see.