I posted this awhile ago, and I still think it's possible, especially after learning that cinder blocks might've been used in the crime.
We've speculated that the cinder block was a simply a prop, as in a stage prop, to implicate Joe, which is altogether possible. The logic is that it wasn't necessary to hold the door open to carry a child through it. Well, suppose they really did use the cinder block as a door prop but forgot to move it. Then Misty noticed it during the 911 call and on a whim told the operator because she thought it added to the story. But if you used a cinder block to weight down a child's body in the river, you wouldn't want to draw attention to one, would you? You'd stash it before LE arrived. Unless you're a mastermind like Misty. I know Ron's anger sure escalated quickly when Misty started talking about "the brick" and the 911 operator questioned her about it.