That Robby story is beautiful. However, as a musician (and piano teacher) I was a bit skeptical, especially when a kid who could barely play, suddenly was able to play a concerto. And while I have heard students play their part of a concerto at a recital, it isn’t usually done without accompaniment. Further, a piano in the Murrah building? Not impossible, but not likely.
Finally, checked it out with snopes.com. Sorry, this is also false.