Nobody has witnessed anything. It's still in appearance the little white wafer that was put into the chalice. Not raw flesh, no real blood.
All that's happened is that millions have watched, perhaps on a daily basis, priests CLAIM to have changed a little white wheat wafer into the literal body and blood of Christ.
Since no change in physical appearance has occurred, no one can legitimately claim to have witnessed it All they can claim to have seen is a man going through the motions of claiming to have done it.
I have witnessed it hundreds of times. Are you calling me a liar?