First of all, Off Topic... sort of. This actually reinforces my point of people not taking someones "word for it" and having such vast amounts of information right at their fingertips. So kudos for that.
I completely agree with you that groundwater and condensation are possible explanations. I don't have time to do in-depth research as I am currently at work but will jot down some finds.
More recent German climatologists Rudolph Kuper and Stefan Kröpelin claim that 'we' may have miscalculated when rain fall last occurred in that area and there may have been rain as late as Dynasty 4 (2613 to 2494 BC).
Robert M. Schoch, a geologist and associate professor of natural science at the College of General Studies at Boston University "Points out that fragile mudbrick structures nearby, indisputably dated to Dynasties I and II, have survived relatively undamaged, indicating that no heavy rainfall has occurred in the region since the Early Dynastic Period, and nor was any heavy rain anticipated by those Early Dynastic Period communities who built those structures."
So really I mean obviously some theories are possible, but there is also evidence that counters one another. Never the less there is obviously ongoing debate about what really went down. I for one really wish that the 115,000 some odd casing stones were not removed in the 1300's or 1600's during the Cairo earthquake in order to rebuild the city and fortresses, as they were all inscribed and all of those inscriptions were removed. Who knows what stories they told. People also claim that there must be evidence of the earlier civilization in order for it to be even a possibility. But if it happened to be as old as the last rainfall what would really be left after exfoliation from sand and the rest would be buried as the vegetation surrounding the area would have decomposed on top of it theoretically. I mean we really do find new structures that have been buried all the time that change what we have written in history. For me there is just not enough factual evidence of one side or the other for a theory to be ruled out. There are many architectural structures across the globe that we can't for sure figure out how they did it, yet we have smartphones.