Below applies to keelboats, only.
Yep, she apparently had a "knock down", where the mast touches the surface of the water, generally meaning that the boat was over 90 degrees. Virtually any modern keelboat will right itself from that position, barring severe structural damage. Most boats on such a voyage will experience such an action, and are built for it. Just from the knock down, there is virtually no sinking danger.
Much more problematic is if the boat turns "turtle", when the keel is sticking straight up, and the mast straight down. Unfortunately, there is a bit of stability in that position, and the boat can stay there. However, the action of waves will almost always push the boat out of that stability window, and the boat will right itself.
ASA 101, 103, 104, 105, 110 instuctor.