What is the ruling if a worshipper falls while intending to prostrate and his forehead touches the ground?

Primary text

If a worshipper falls while intending to prostrate and his forehead touches the ground, it suffices, even without forming the intention (niyyah) at that exact moment, unless he cuts off the intention of prostration. If he turns onto his side and then turns back so his forehead touches the ground, it does not suffice unless he renews the intention for prostration. The distinction is that in the first case, he remains within the established manner and form of the prayer, while in the second, he has departed from the Sunnah posture, necessitating a renewal of intention.