Did they JUST see what happened in the flashforward or do they also remember their memories of the future (if that makes any sense)? Because from what I saw, people seemed to only know what happened in those 2 minutes, plus their frame of mind during that time. But they didn't know why or how it had come about. For example Olivia doesn't know who her future lover is ans has no idea where he comes from, let alone his name. So it's a bit strange for the boy to know who she is already (unless in his flashforward he had a picture of her with her name under it to look at).