I think JS admitted to leaving the message, saying MS condition had worsened. Maybe RN deleted it after listening to it, or someone else did. Have to wonder why she didn't call him back. If she could have neutralized things with JS, then she wouldn't have to commit suicide.... She had the phone in the room as she set things up, so you would think she wanted to keep in touch. You do have to wonder if it was not a nice message and JS deleted it when body found - as would make him suspect or appear to be a jerk. In accord to prior wives x2, he had a temper and this would certainly upset anyone. However, that is only speculation since anyone at the home could have deleted it. The LE would most certainly have asked the main players for their phone records and determined who called who and where they were located throughout the night based on pings. One odd thing- most phones will let you recall erased messages - so, if her phone had that option and someone took the time to delete that, then it may be suggestive of malice.
The phone journal is part of the latest smart phone capabilities that act like a phone, camera and home computer. People get very attached to these phones and carry them everywhere - to the bathroom, to bed... - so they tell a lot about the owner. The mobile phone owner can go the App (application) Store and select 425,000 apps dealing with anything from games (ex Angry Birds), music, weather, facebook, daily journal, etc. You name it, and its there. So, she must have had some type of journal/diary app that had some sort of comment that had been typed in - about being upset. But, the LE can't figure out the dates, or who entered the data. Just plain odd.