Relative to the tread distortion:
In spite of the fact that you think you may not have hit anything, it is possible to run over an object and damage the tire, but not know that happened - and based on your description, that is what happened. This can happen to any tire regardless of brand.
I had a friend who rolled over an 8" long wrench that penetrated the tire - and stuck in. The only way he noticed it was by the feel of the car and when he stopped to investigate, he heard the hissing. You would think that something that big would have been seen laying on the road - and you would think that something that big puncturing the tire would be noticeable when it happened - but that is not what occurred.