Well she is still alive or if she isnt she may well have been murdered but we may well never know who by ? On the other hand there is a third option that she wandered out of the apartment and met with an accident ? Remember the doors were open. There were roadworks in the street next to the apartment. This was my very first theory when I first heard the story. Why did they mention the roadworks ? I believe she wandered out to find her parents and fell into the roadworks and was covered up next day.

Yeah, Skidoo

Yes, but she won't remember who she is because she was taken at such a young age. I can't imagine what the parents have been through.

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Yes, her parents do and will continue to believe it until either she is found alive, or evidence is found that she is gone. What else could parents do?