I think a complete lack of evidence is what’s really hindering the case. Dulce’s mom wasn’t paying any attention at all, and she had done the same thing in the past in that park so in her mind they the kids would be fine playing where they were. So she saw nothing. I’m not at all saying she is to blame but it’s a fact that she saw nothing.
The red vehicle has been investigated and has no connection. The people playing basketball...well, I think they tried their best but really had nothing helpful to contribute. They were focused on their game, and unless Dulce was carried away making a big fuss, there’s no reason they would have noticed anything unusual. Seeing someone walking away from a playground with a child, or even running away, wouldn’t make me think twice. If they were running, I would assume the adult was playing a game with the child, so even if the kid was making noise I wouldn’t automatically assume something bad was happening.
If there are people who know something, they would have found a way to get that info to cops by now if they felt the obligation to do so. There’s either no one who knows anything or no one who is going to tell no matter what, so LE really has nothing to go on.