Three things:
The ping list does not appear to be a "tracker." It only offers hits when the phone make/receives a call/text. So in each case, you can assume the phone is getting a call or making a call when it pings off a tower. I don't know why it doesn't show his movements when the phone isn't in use, but it doesn't.
In some cases, there are several calls between tower pings (I don't have the doc at home, but I can give more details tomorrow), yet the phone doesn't show any tower info. For example: Call 1 from 555-1212 at 3:00 p.m. pings on the Whitney Ranch tower. Call 2 from 555-1213 at 3:05 p.m. has no tower info. Call 3 at 5 p.m. pings off I-515 and Russell tower. I believe there is no tower info because there is nothing new to report (it's pinging off the same tower). This is significant because, in my opinion, it means the phone hasn't moved. If this theory is correct, it means the phone sits at I-515 and Russell for several days before losing communication with the tower. (I should really have some of you LV WSer's come to my office to see the doc and know what I'm talking about...)
Finally, I do not believe he ran off with someone, or for that matter, walked away from his life. First, I cannot stress the remoteness of the neighborhood where he dumped his car. I used to live downtown and a dumped car could go days without being noticed, maybe weeks. Second, when looking at his email account, I believe he only thought about one thing: finding a job. I am not exaggerating when I say there are thousands of emails in his account, and 99% revolve around looking for work. Finally, despite what some believe, the family ties are very strong. Sure, he moved to St. George, but the drive isn't that big of a deal. I just don't see it.