MacBook Pro 15" Retina display was broken inside

My daughter has a MBP15" with retina display and she found retina display broken on the left bottom area inside without any damage of outside screen surface.

It looks like several burnts inside.

And she went to Apple store, but store employee told her that it was caused by my daughter's fault like inserted a kind of hard material and closed the display. So they asked almost > $700 to replace it.

So I am wondering how come a hard material made internal damage only without any minor scratch or crack outside???

Does anybody have any idea about this?