Abeta- Regarding your #2, it is possible but no way to know. If you are correct, this would create a messy situation, because if they did find even one of these missing people, that would change their topline results (and I doubt they would want that to occur). So, my hunch is that the information they lack is secondary data. That is just a guess though. I think at any point they can just decide to call the lost to followup cases truly lost and not to pursue this issue further. That way they get closure.
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