For the sake of argument, let's say that Casey stormed out of the house with Caylee on June 16th.
Let's say she wanted to go hang with her boyfriend, but not with Caylee in tow.
Let's say she did leave Caylee with someone, but not a long-term "nanny", and definitely not someone she should have trusted her with.
Maybe this person did take off with the baby because Casey was an idiot to have left her daughter with her in the first place.
All the lies Casey has been telling may be to cover more than one secret.
The lies about employment might be because she's making money illegally but doesn't want to admit it.
The lies about the nanny might be because Cindy left her daughter with a drug buddy she barely knows, and has no way to locate, but she doesn't want to admit that she put her daughter in danger when it's easier to just lie.
But I can't get past the decomp hits.
ETA: Unless -for the sake of argument- something bad happened to Caylee with the drug buddy babysitter, and instead of picking up her daughter, she retrieved her dead daughter's body and has spent the last month hiding the fact that because of her negligence, her daughter is dead.