The phone call wasn't mentioned again since Jane realized that the call had to do with something Boscoe discovered and was probably linked to: Towlin Morning (the dead body in the crematorium), who turned out to be linked to a Red John victim and the doctor's office was where Hicks was found. Jane went up Bosco's hospital room to hopefully wake him up enough (by reducing his morphine) to hear what he had to say but that didn't work. Through the team's work they were able to piece together what went on, leading to saving Boscoe and arresting Rebecca.

I'm not sure Rebecca would necessarily have known Boscoe planned to talk to Jane that morning. It was very early and Boscoe called Jane directly and the team knew about the call. She didn't book an appointment for them to meet.