I found this interesting in what Rick wrote:
The pool is the logical explanation. Cindy said the steps to the pool were put away yet they appeared the next evening when she got home from work.(on the 16th) Makes sense to me. i think Casey paniced and hid the body in the shed until the 18th when she backed into the drive. She put the body in the trunk and drove around a few days to find a place to hid the body. The woods by the airport is where she probably put it. I think the 17th when the cell phone pinged there by the airport is when she was just scouting for a place to put Caylee's body. That is my theory.
If I recall, during the OTR interview Cindy told Greta the 17th is when she found the ladder in the pool.