Caranca Meteorite (Peru)

If the impace has vaporized the triolite and produced the illness in the local people the first days why theres no signs of impact metamorphism in the crater, impact brcias, glass, etc. I only have sawm in the crater chaotic blocks of the cenozoic soil, mud, etc but no evidence of impact metamorphism. and how has survived this fragile rock to the entry thru the atmossphere? thanks