TS idea of returning to retrieve Gannon days after his death also seems odd. It is highly risky, and she would be paranoid of being tracked. And if she was worried about the disposal site, why not just cover up better at the original location.
Unless there is an unknown person; the list of potential accomplices is small.
I think it is very possible that Gannon was alive on Monday, and someone was responsible for taking him to Florida, then or in the days after. And he died in a second person's hands.
'Why are you saying Gannon is dead?' He is not dead. We are going to find Gannon.'
A possibility.