It's been more than 72 hours since she went missing.
They could be several states away, so LE needs to be putting out APB's in a much wider net than just Illinois or Arkasas. I'd be thinking Minnesota, the Dakotas, Kansas, Nebraska, Oklahoma, Texas, Indiana, Iowa, Kentucky, Tennessee.
Most likely, they are hiding out in a cheap motel, where she is not going outdoors and he is doing all the food shopping and such, in his 2013 Black Buick LaCrosse. I'd think small towns not near the interstate freeways.
First of all, I'd be checking any place where he has been known to be spending any time in.