I think Casey would have hit the road if she had been given 24 hours. I don't think she would have ever told anyone Caylee was anywhere except having fun with her nanny. According to Lee, Casey didn't mention anything about not knowing where Caylee was until he said that LE was on the way and would ask to be taken to see Caylee.
If you are staging a kidnapping you don't leave items from your PARENT'S house with the body.
That and especially the duct tape will be Casey's undoing. Not only does the duct tape show malice, I think the adhesive side will be covered with evidence that will show it was put on in the Anthony house.
JMO