Isn’t this sort of taping considered to be bugging a private conversation since the taper was on neither end of the conversation, it was not in a public space, and neither participant in the call was aware of it?
I don’t know the law on it, but they turned it in anonymously, so they can’t get in trouble. However, I wonder how big the circle of people with access to Ross’ office was and if they know who would have been in the office at that time. This is not a big deal, so I doubt they will put effort into looking for this person who is most likely completely unrelated to the leaks we are seeing right now.