apparently you do not understand that a 'walk around' was not possible! They cannot space walk outside of the confines of the cargo bay under any circumstances unless tethered to the robot arm, which this shuttle did not have.
Secondly, pictures were taken of the external fuel tank and were going to be examined by NASA upon return. Pictures of any damage to the orbiter could not be achieved in space.
They (mission control) had taken pictures (visual check) of previous missions using telescopes yet declined to do so in this case.
I'll stand by my assessment that mission control screwed up by not doing a visual check. Like I said in a earlier post , the debris impact may or may not have damaged the left wing.
Since they didn't bother to check it out to their utmost ability, it'll just have to be a question that naws on them while they lay awake at night. Action or lack thereof when other people's lives depend on what you do has it's consequences.