When the Columbia broke up at hypersonic speed, it is not unlikely that the environment was filled with shattered pieces of flaming metal going in all directions. It would not be surprising to find many signs of gouging on tiles found downrange of the breakup. If this is the tile found near Lubbock, I assume before the main breakup occurred, the gouge may be significant. The gouge appears to have been eroded by heat which would not be the case if the gouge had been the result of impact with the ground. As a comparison, note the clean chip on the lower right, which is likely the result of ground impact.

The heat damage at the front edge looks very interesting to me. There appears to be molten metal in some parts of it. I would give a lot to see this tile flipped over so I could see the back.