Yikes
Glad you got this sorted but did they say nothing about the frame size/amount of seatpost showing? IMO if that is the normal seat height then the bike is too small for you and the extended length of the seatpost may have caused or contributed to the failure of the frame.
With the amount of leverage the long seatpost will be inflicting on the frame I'm not at all surprised the frame failed in the way you describe.
Anyway, good result and keep on riding