even a slight nick or scratch can cause a weak spot. then when the stresses are just right it will break. It also could have been a manufacturing defect like a slight fissure in the blank or a weak spot in the roving.
How deep was the water where you where fishing? You could make a rake from some wire like a closet shelf and some pvc pipe or even weight it down and use a rope to snag it. Then you may be able to determine what caused the rod to fail or even have it repaired or replaced under warranty.