If you think it was in some way faulty then we will be happy to look at it for warranty.
For future reference, flange failure like this is typically down to low spoke tension. Wheels need to evenly distribute the load over all the spokes, so as they get loose they can ramp up the loads on individual spokes/holes and start causing fatigue. With a new-ish hub this usually breaks the spokes, but the fatigue can get to the flanges more over time.
I hope this helps and seems reasonable.
G.