I say of virtually every criminal that they forget what they aren't supposed to know.
Let me explain.
JFd was missing. That's all anyone was supposed to know. Missing people are usually found, off doing something. They weren't missing, they knew where they were.
So the task is to locate them. As we saw in the SMorphew case, everyone was frantic to locate SM, racking brains to guess where she might be. As people do. Most people want their missing person found. It was only the husband who led with reasons why she would be gone for good.
IMO FD and MT led with alibis. You don't need an alibi if there's no crime. You don't need an alibi if the missing person is sidelined somewhere with a running injury.
They led with alibis, scripts, selfies and lies.
Granted we haven't heard entire interviews or much from FD at all, but you know what we haven't heard a word of? -- genuine effort to help locate JFd. Phone numbers of friends, awareness of any of her routines, brainstorming.
FD's text exchange with LA is glaring for the same reason. He's asking her if there's any news (knowing full well JFd isn't going to be found, not readily anyway). Not one word in those texts of what he's accomplished in trying to find her so far and of what he's tackling next. No list of hospitals called, no list of contacts called, no game plan to help search.
FD and MT forgot what they weren't supposed to know. They forgot to take on the roles of worried family members, desperate to help in any way possible. Did you check here? Could she be there? Who else might know where she could be?
The natural checklist for families with missing persons who want them found.
Welp.
JMO