I think Hayleigh died due to complications from something that triggered her Asthma, and MC had no experience with a child with Asthma. This happened either the day before, or during the day before Ron went to work.
Misty couldn't take her to the hospital, because it was drug related. and Misty is underage and not her mom. So, Ron would have to show up, admit he's living with an underage girl, drug related, and child would be considered endangered, Ron would lose custody, and court was just a few days away.
Haleigh couldn't breathe, and she died while they were trying to figure out what to do. Ron called his cousin the Air Conditioning cleaning guy, so he wouldn't lose custody of Jr, and he was owed a lot of money from Crystal.
The man in black bouncing the couch was part of the cover up. Hayleigh was already gone. Jr. saw the man in black.
Whoever took the van hid or burried Haleigh.