Need help getting daughter back?

I was granted full legal and physical custody of my daughter back in 2004. The summer of 2006 I let my daughter visit her mother in Illinois, he mother never returned her to me. (I live in Alaska) At first I thought it might be good for them to spend some time together since her mom was doing much better and I was preparing to move, so I told her she could stay there for the school year. Well, come summer 2007 her mom refused to send my daughter back. I've tried getting help from both AK police and state troopers, and Illinois sheriffs department. Nobody can help me or tell me the proper way of getting my daughter back. They keep moving every three or four months that I can't track them down. How can I get help? Who should I report this too, as law enforcement doesn't seem to care?