It's hard to figure out why that happens...But I hear this all the time...Ball may be store in a closet or like you said, just on the floor in a room...Usually when this happens, temperature may be the reason...That closet or room could be too hot or too cold...Or both...
One of the main reasons balls crack is due to a rapid temperature change...They went from hot to cold to quickly, or from cold to hot to quickly...
Then we hear about people who leave their balls in the car all winter... And nothing happens to them... Go figure...
But for the most part when a ball cracks, the person says the ball was stored...Maybe in a room or in a closet...
Over the years we have even had a few crack while sitting on display...
Now most companies have a warranty period...Hope your ball was still under warranty...
jls