Where do I go from here?

I'm so pissed at our justice system. One state in particular has failed my daughter miserably. My ex husband admitted to someone that he SA my oldest daughter through out the pretty much the whole marriage. I was told about it and asked my daughter and she confirmed it. She had a 2 hour interview (the detective said it was the longest and most detailed interview he's seen in a while). This was almost 3 years ago. 2 states were picking up charges, but one state in particular had access to physical evidence. (I left my abusive ex with a backpack for each kid and myself and took a plane back home). All of our belongings were still at my exs house for about a year into the investigation, the detective didn't even bother with the case, and all of the physical evidence went up in smoke, literally, after he was evicted from the home. The landlord burned everything that was left... OK maybe we'll recover... nope... just found out the girl he told has died and she was NEVER interviewed by police. So the one and only witness to him actually admitting to it has died. I'm just at a loss about what to do. I called the lead detective on her case in the one state but he hasn't bothered to contact me either. They are leading the investigation and it's like I keep hitting a brick wall every time I turn around. Even his own daughter had admitted he done the same to her too, but she now won't admit to saying it and her family is covering it up too. If anyone has ever been in this type of situation, where do I go from here?