The tip from the milkman sounds promising. I'm sure they must be running the plates for neighboring states. If the car was a clunker as described, then the guy probably didn't drive it from very far away. And he may also not have been able to go far after the abduction, if this car doesn't run very well. Unless of course he ditched that car and switched to another one.
And another article reported that the younger sister said that Elizabeth asked the man what he was going to do to her, and he said he "might hold her for ransom." But if that's the case, it's ominous that no ransom demand has been phoned in yet.
And if he wasn't sure what he was going to do with her at the time he abducted her, that also doesn't sound good to me. If he had really been planning on a kidnapping, he would have been better organized.
There's a problem with the alleged license plate number 266 RLA. Utah issues license plates alphabetically. Currently they are at L or M. The present format "3 digits, 3 letters" has been in use for about 15 years. Before that it was "3 letters, 3 digits". Therefore it is unlikely that the plate 266 RLA has been issued in the past 25 years.