Why do you say the reported sighting/texts MUST be correct? IIRC, there were some doubts about the accuracy of those reports/
Evidence is evidence. The prosecutors do not seem to be in doubt as they limit the window of opportunity as being between 3PM and 5PM, meaning they are confident that HD was alive when SA returned home from Big Spring and they are confident of SA's whereabouts after 5PM. That is what they have to work with and the main reason why they don't have a case, it is too short.
That and the fact that their corroborating evidence turned out to corroborate nothing when the FBI looked at it, lol. Must have been a gloomy day at the office when they got THAT report back.
You personally can doubt all you want, it is a free country, but the fact is at least three people reported seeing her that day, and there was telephonic communication by her as well. And those are just the ones we know about, there are likely others too. I think you are going to find that the activities of the principal characters that day have been witnessed by MANY people, not just the ones we are aware of.
Plus, I suspect that at least two individuals who initially publicly claimed to have had no contact with HD that day subsequently changed their story when confronted on the facts by LE later. There has been lots of lying going on in this case IMO, just way too many events that don't make sense otherwise. So, ya, I think at least two in my opinion, maybe more.
So I think the prosecutor is on pretty solid ground when he says she was alive at least until 3PM.
But, unless there is a trial, we will never know the details.
One more thing, I would not be in the least surprised if there is significant disagreement among LE themselves as to exactly who is responsible and what happened. Some of them act like keystone cops, while others are professional, there are going to be rumblings for sure. The second group is going to be horrified by the antics of the first group.