If that’s all you’re getting it from, then you’re in trouble. We don’t allow parental moves such as adoption to negate regular citizenship status, and I certainly don’t see the precedent that has been established on that re NBC status.
There are several ways to lose one's "natural born" citizenship status. Adoption by foreign parents and acquiring citizenship in their country is certainly one of them. Once lost, the status of natural born citizenship can never be regained.