I know of the practicalities, but something has to be done. They can`t go on using the current method really.
Though if they had a small drone fitted with a camere and using a remote link to the shuttle, they could manually inspect the exterior. It does look likely it was the insulation hitting the leading edge of the left wing though.
Only STS 107? I`d have thought they`d done much more than that, by now. That means they`ve only done 29 missions in 7 years. Thats not many especially when they are making the ISS.
If you want a book on the shuttle get the one written by some guy Jenkins. I haven`t got the most uptodate edition yet, as it only covers missions upto STS 75. Though it does cover the development and specifications of the shuttle so well. This will just create another section in the next edition like the Challenger section.
I had a plastic model of Challenger at the time of the accident. I wish I still had it.