You know, I think it could actually have been her mom's number, although I can certianly see casey having a guy or two on the side. But, when I first read that, I felt she wanted to know to go outside sop Tony would not hear her arguing with her mom or making up excuses about where Caylee was. That would have screwed things up for casey especially since she had been telling Tony (or his roommate) sometimes that the child was with CA. "What was that all about? You told us Caylee was with your mom? Why is she asking you where she is and why are you telling her Caylee's with the nanny when you told us Caylee was with your mom? What's going on here?" She wanted to avoid that. Special ring and she knew to go outside.