I agree, I think even if she had left the body there in a panic, she would have returned soon after to move it to a much better location far from her parents' house where it wouldn't be found. To me, the body being placed there seems to indicate a different perpetrator, one who either didn't care about the body being found or who actually wanted it to look like KC was responsible. Either that or she really suffers from serious enough mental illness that she could put the body there but not remember it. If she had killed Caylee (or even if she just wanted to conceal that there had been an accident, or to cover for a paramour or other friend) I think she would have moved the body someplace else, any more remote area, any pond or whatever.