Me too, and I would hang on to those pics. I think there's a good chance the builder may not do anything other than finish out the house. Whoever buys that house and perhaps experiences flooding would be very grateful to have evidence that the builder knew before the sale that flooding was not just a possibility, but a reality.
That's what I figure as well. They will go ahead and finish the house and sell it to some unsuspecting buyer who doesn't know enough to do their homework. They'll give themselves a big pat on the back about it too.