I don't find it weird that the ex filed for divorce. She obviously left him. She was pregnant by someone else. It's usually a financial matter. She used to work at McDonald's, so I'm guessing she didn't have the money. The person that files first believes that that will give them an advantage in court. I've seen it before. . .a literal race to the courthouse.
MOO, this is a pretty clear case to me. She dropped the bf off at work. Was he on time? Did he work? She's in the middle of a divorce. There are children involved and she is now pregnant with a bf's baby. She had plans to meet the ex in a public place. She's never seen again and her car is found a short distance from the ex's house. Now LE is processing the ex's car? No surprises here for me.
I think anytime there is a divorce, it can be a dangerous time for the woman, regardless of the history. We see it repeatedly here. I'm always reminded of Crystal Brame. Her husband was chief of police, for crying out loud! He shot her and then himself in front of their two children in a grocery store parking lot.
http://www.learn-usa.com/transformation_process/law_enforcement/Brame.htm
ETA-As far as the bf, I think he's "strange" (read:drug affected). But if LE didn't find him truthful, I don't think they would be processing the ex's car, kwim?