Pyramids, being rather large, are not really the kinds of things one expects to be lost easily. And yet! Seventeen new (well, not "new," but) pyramids have been identified through the use of satellite imaging, which can see underground.
Everyone knows that pyramids were built by aliens, so it stands to reason that they'd be visible to advanced technology in space. But no one seems to have tried it until University of Alabama archaeologist Sarah Parcak, who's pioneered the use of satellites to find previously undiscovered archaeological sites in Egypt. Because ancient Egyptians and their extraterrestrial overlords constructed buildings out of dense mud brick, infrared imaging will show the outlines of those structures against the less dense earth that now surrounds them; archaeologists can then use those photographs to map out their plans.
So far, Parcak's work has concentrated on the ancient Egyptian city of Tanis, located at an area near the city of San El Hagar. But she thinks that more sites are waiting to be discovered with the same technique. Including, possibly, more pyramids! And, if we're lucky, a UFO.