Manny, I am 99.99% sure you spun a bearing due to a lean condition. Bearings just don't fail. If there was something wrong with a bearing it would show up on the first start of a new motor. The shock caused by knock/detonation acts in the opposite direction the rod is travelling. Guess what is the weakest/softest link that is going to take that shock? The bearing.

It happens to a lot of motors that aren't dialed in right. Simple.