Columbia
At launch, the left wing (the one which broke and caused the ship to break apart) was hit by foam debris coming from the external tank. At the time, Mission Control did not consider that it had caused a serious damage to the orbiter -- and from what I read all around it's not even clear that they informed the crew at all. What I don't understand is why a crew member did not fly around the shuttle to make a visual inspection before their reentry in atmosphere. Especially in this case, with NASA knowing that the foam debris could have caused damages to the wing.
I'm a completely clueless padawan in this matter, so this idea may be completely stupid. The damages could be completely unrelated to the launch incident. However, when I head off for a significant car trip, I inspect my car. Can't they afford a visual inspection of a space shuttle?
