Is it a Kansas state law on a new construction home for a contractor to disclose any flooding.

Since this is a new home, the builder is not obligated to provide a disclosure statement similar to what would accompany the sale of an existing home. On the other hand, you have the right to expect a "as new" home. Given that it was a pipe break, it is certainly fixed and no longer leaking. Once the drywall, framing, insulation, etc., is dry, you should not have any mold growth related to that pipe break. Keep in mind that all houses will get mold spores in the house and if they find a generally warm, wet location with organic material, they can grow. If you are concerned about some unseen condition existing in the house, hire a reputable home inspector to look into it. The cost is relatively small for the peace of mind.