I hate to say this, but Maddie is 99% sure to be dead. The size of the appeal, and the worldwide interest shown in the case would have made it too dangerous for the kidnapper to keep her alive. She's more than likely buried in some remote Portuguese hills/countryside.

I'm not a parent, but I think I'd prefer to think of my child as passed away, rather than being in the hands of a paedophile ring for the last x number of years. I also think that how they left their young children alone in that apartment that night was verging on a criminal act in itself.