I always carry a spare belt in the trunk, I've had to replace too many over the decades to not have one always with me. Blowers put an enormous amount of stress on the belt and pulleys and it is not uncommon to have failures of this nature. Do you run the stock tensioner? Was it the actual tensioner pulley or one of the idler pulleys that seized up? I should have been some squealing before it failed as the bearing went out. I run a Thumpracing tensioner and have replaced all my idler pulleys with a set from Metco. They even swapped one of their pulleys in the kit for a larger one to match up with the Whipple one.
I even have a dented hood from once when a belt shredded halfway and flung itself against the bottom of my hood at 5K rpms's
So to answer your question it is not normal but it is not uncommon. Be prepared (Boy Scouts).