I got an email back from a nice lady called Elizabeth Sobol. She said, and I quote:
Thanks for your note.So, there you go. If you ever wondered whether that Izthak Perlman 'with what remains' story was true, there's the answer.
We have had many inquiries such as yours. As such, I have had the opportunity to ask Mr. Perlman about it and he has confirmed that the story is not a true one.