Some thoughts about the final phone call Jennifer made to Rob in the evening of the 23rd...
During this call, Rob said they had a disagreement that was typical for any couple and that Jennifer told him she heard a knock at the door, believing it to be "the upstairs male neighbour." I always wondered what this disagreement was about and never saw him elaborate on it until I read through most of this thread and saw this post by marable...
However I still have my own theory. I wonder if Rob actually heard the knock at the door and questioned Jennifer about it - e.g. "Why is someone knocking on your door at this time?" or "Who have you invited over?" or similar accusatory questions. I'm not trying to paint Rob as a controlling, jealous type at all. I don't know him or what he was/is like as a partner, but it's just a thought. When you consider that this phone call was very brief, only a handful of things could have caused a "disagreement" in such a short space of time. Quizzing her about the door knock - or, now that I have learned, the unreciprocated "I love you"comment - are things that would make sense here.
What also pushes me in that direction is the fact she specified it was a male neighbour. Did this person knock and call out to her when she didn't answer, and this male voice was heard by Rob so she had to explain it in some way? I noticed a few sleuthers speculating she likely knew who was knocking as she didn't check to see who it was and that she may have been seeing another man/men. Maybe this man was at the door, or it was her ex-boyfriend who was out drinking at a nearby bar that same night. She may not have wanted to explain why an ex was there?
I'm fairly sure that whatever the disagreement was about isn't of any importance/relevance to the case, but it might give some insight into whether Jennifer knew the person knocking or not. With her phone still pinging off different towers after this call, it suggests she, or the phone at least, went out right after hanging up the phone... possibly with this mystery visitor??