It's fine to disagree but I believe I said "usually" which means in most cases, but not all.
Ask someone in LE who actually works in missing child cases. Most of them will tell you that when it's a family member who is responsible, LE is more likely to figure it out quicker than if it's a stranger. There are going to be signs of guilt or remorse for what they've done, whereas a stranger predator is not going to show much remorse at all. Other things come into play as well, but each case is different.
It is my very strong opinion that if either of these parents were responsible for their daughter's disappearance, LE would have arrested one or both of them by now. It's not that hard to get an arrest warrant if they have enough probable cause to hold them. They can always gather more evidence while they're sitting in jail. My guess is they just have not found anything yet that points to either one of them.
