Timing is wrong. Two weeks apart. Stories now indicate that second car ("large white object") has been located, but no location given.
Actually the Fresno County Sheriff pdf (link above) says,
"
Deputies and officers found some vehicle parts in the water about 40 yards upstream from the red car. At this point, we
are unable to determine if the parts belong to the white Ford Focus."
The Ford Focus' plate was found during the red car crash investigation, but not connected to the second couple until several days later when they were reported missing.
