After months of looking at this case I do have a theory.
First I have to say that I would not be surprised at whatever the truth may be, if it ever surfaces, so I could be totally off base here. Regardless, here's my attempt at it:
As far as we know RC has an alibi. He was at work and until that is proven otherwise, I can't get past it. Also, GGS adds to his alibi by saying that she saw Haleigh alive and well around 7:00 p.m. (again, something I can't get past until we know otherwise).
I really do think that Misty had a hard time getting Haleigh to sleep that night. She had just returned from her 3-day drug binge and she's in no mood to mess around with an uncooperative child. She calls Ron at work (like she did on prior occasions as fellow employees have stated they overhead Ron at times give Misty permission to discipline the kids).
Ron is thankful Misty is back home to watch his children and he knows what kind of shape Misty is in after her 3-day binge, so he tells her to give Haleigh something to put her to sleep. Misty miscalculates the drug dosage given to Haleigh and she overdoses. If Jr. saw a man in black bouncing on the couch at the MH that night, I think it was someone trying to give Haleigh CPR.
What makes me believe this theory about a drug overdose is a certain interview where, when asked what might have happened to Haleigh, Ron looks at Misty and very defiantly and somewhat disgusted says, "I don't know, I was at work." It was the look he had on his face that gave me the feeling he was in the clear as to the actual "hands on" accident and Misty was the one who screwed up.
I also believe this because I feel that RC has to be culpable in some way to behave the way he has been behaving throughout this whole investigation. Although he did not actually give Haleigh the medication (in my scenario), he would have been the one to give the order to give it to her. I also believe it was some sort of drug that would have no business being in a child. This is why they couldn't take her to the hospital and say she accidentally got into the medicine cabinet.
I think there was then the flurry of phone calls as to what to do about the situation. They had to remove all illegal drugs from the MH, wash any and all blankets that Haleigh might have vomited on and of course do something with Haleigh's body, stage the bricked side door, record RC on the store video after work, and for the 20 or so unaccounted for minutes prior to calling 911 - discuss what was going to be said to the 911 operator.
If you will recall RC's performances for the media the following day, they were indicative of someone who had lost a child, as in death. If she had been "stolen" I would have expected him to be very anxious and giving out as much information as possible about Haleigh, the situation, etc. His 911 call is also very telling. My analysis of that call is somewhere around here at WS. Not once did he give any helpful information to the 911 operator. He was very uncooperative.
As to Haleigh's body, I truly don't think Misty knows where it was taken. I could be wrong (on everything frankly as these are just my opinions), but her various tests show that she doesn't know where Haleigh is now. Based on the activity of the search and cadaver dogs, I have to take into consideration the water and also the dumpster. I think it's possible the tracking dogs could have picked up Haleigh's scent from playing earlier in the day as to the shed and the water, but the dumpster is a different story. I think perhaps someone put Haleigh's body in the dumpster and kept watching and waiting for it to be emptied. After a few days when they could see it hadn't been emptied, they moved her body.
Sorry this is so long. Thank you to anyone who read the whole thing.