I think this is another example of where biblical literalists are willing to believe in the absence of evidence. That's fine, but it's not particularly rational. Certainly Judaism and Chritianity do not depend on whether the Exodus story is factual.
Except that most of the "plagues" may not have been that big a deal. For example: the Nile turning red -- the upper Nile, anyway, often turns a reddish hue during the annual flooding due to minerals from the Abyssinian lakes. Frogs and flies often swarm during the flooding. "Cattle pest" causes painful boils in both cattle and humans and did sometimes appear extensively. The darkness is caused by the Khamsin wind -- remember when during the Iraq war there were a couple days when day turned as dark as night due to the windborn sand?
Basically, every single plague except the "death of the firstborn" is not abnormal. So it is quite possible that even if they all struck in a short period, while it would definitely cause unrest I doubt that anything would be carved into stone about it. As for the death of the firstborn, that would be supernatural and you would expect that to be recorded. You can believe it never happened and so of course was never recorded, or it did happen supernaturally and was possibly supernaturally suppressed from being recorded. After all, if it really DID happen, and God caused it, then the logical corollary is that yes, Satan also exists and might have a vested interest in suppressing any recorded evidence. You basically get God and Satan in the same package in both Judism and Christianity, so....