I think the same thing, though I lean towards the Sawgrass dumpster on the 17th or 18th. For her to have had or moved the body between the 24th and 27th I think they would have a lot more forensics.
I think the Amscott abandonment and purse left in the car, along with all the Blanchard park references was her original plan for Casey to dissappear. On the 9th the joggers body was found there, Casey mentions that her mother was concerned for because Casey jogs there, she says she lost her phone there. If she hadn't gotten distracted with Tony and done her normal lack of follow thru the plan could work like this: Dump her car with the purse in it (just like the joggers was found), car is recovered, they may or may not be able to tell Caylee is dead, but Casey is missing. Suspicion goes toward the park attacker whomever he may be. Maybe she really did run out of gas at Amscott, maybe the plan was to dump the car at Blanchard and she didn't make it.
Someone may have found that phone and have no clue what they have. They should put out a reward for it.