Why would someone have to steal the car to place a body in the trunk?
If KC was the perp, I still think she would dispose of the body in a place far from her parents' own neighborhood, and a remote place where it would be much less likely to be found, she wouldn't want to spend her life in prison, much less even admit to her parents that Caylee was dead. I think since she drove all over town all the time, and there are so many lakey, foresty places to hide a body better, even if she had dumped the bag there in the neighborhood in the first moments of panic, she would have moved it as soon as possible to a less findable location.
But you're right about the incriminating factors against her (mainly her failure to report the disappearance, jmo). Have a good night
p.s. I heard Tim M say on Nancy Grace that it was his understanding the bag did not show any signs of having been buried. That there was just an indentation under it from sitting there for some time, and just a little dirt washed up around the edges. But he was saying that's what he had been told, he had not seen the bag himself. I'm not sure if more has been reported now about this that is different.