There is a post on this thread that states that her mother reported that her badge and orca card (orca is a local public transit pass) were at home.
If I were a 4 minute drive from home, I would go get my badge. I would also offer to take the bus so I didn't hold up the carpool. But I would probably know they'd wait for me. At her level, I am pretty confident that she had some flexibility as to her arrival and end of the workday.
So if her badge was still at home it would suggest either:
(1) she never made it back home after texting her carpool; something might have happened to her in the place she pulled over to send the text, or somewhere along the route home (if it really only takes 4 minutes, that is not a large window of opportunity). The timing of the text could therefore almost pinpoint the time of the crime.
OR
(2) The crime was committed earlier (maybe the night before or first thing in the morning) by somebody in her personal life. This person dumped her body and then planted her car to make it look like she was abducted on her way to work. Even if the murder was well planned, in the heat of the moment this person may have forgot to take her badge to stage the crime, so had to send the text in the morning as a 'cover up' for why there would be no badge with her body. Also, gives an excuse to miss carpool, which broadens the mystery and buys more time before she would be reported as 'missing'.
OR