Nothing – nothing – could have been more important to Mr Ramsey then preventing that phone call. Mrs Ramseys was on the other side of the room? Not an excuse. How did that happen with stakes so incredibly high?<quoted text>
That's a good question, and that is one of the problems with the theory. All theories have their weak points.
One thing to consider is that if PR is next to the phone, and JR is on the other side of the room (we don't actually know where they were) then there really would be no way to stop her. Once 911 is called there's going to be a response, even if the phone is hung up. It doesn't take long to dial 911.