After all (as someone suggested) if there was a problem with tiles (if that ends ut being the cause) there could have during a space walk been the chance to effect a "CAT Q I landing" repair.
Yesterday, one of the AM talk shows interviewed a former shuttle astronaut who had been on a team trying to develop a tile repair kit for the shuttle. He said that no matter what they tried, the adhesives that worked just great in standard conditions did not work in a vacuum. Their conclusion was that 1) any repairs attempted in space would not work and 2) attempting to repair in space would likely damage other tiles in the process, making the situation worse, rather than better.
Only possible solution would have been a rushed rescue mission.