i have not read through this thread because just when i think i'm on to a good idea, i read posts from people smarter than me and i get confused and don't know what to think. therefore, anybody who finds fault with what i'm about to say is welcome to point it out and let me know why these scenarios can't be.
i have two theories: 1. Misty just doesn't remember. She was too drugged up or hungover and that night is simply a blur. I'd be interested to know if she can recall anything that happened after Ron got home. If so, then I change my mind and think chick remembers more than she's saying. Even if she doesn't remember, I don't think this could have been pulled off by her alone so somebody, somewhere should know something.
2. IIRC, back in the beginning of the case the cadaver dogs hit on the body of water nearby but stopped there. Then I read that there was a houseboat fire not long afterwards that completely destroyed the boat. Could someone have taken Haleigh's body and put it on that boat to hide it, then came back later and set fire to it? This certainly would explain why no clues and no body has been found after all this time.