MF's search on the 14th for bodies found in Austin makes me think she had dumped Heidi's body in Austin and went back for it. I hope they could find out where her car travelled, or phone pinged, between the 12th and the 19th.
If she did go back for it, I expect Heidi was in the bag from the very first day. That is what the restraint wording leads me to believe. As regards liberty, I think they were forced to word it like that so that they didn't hint at her being responsible for the murder until they had the evidence. But they seemed pretty sure that they had evidence that MF had restrained and placed Heidi in the bag, and in the trunk, and not another perpetrator.
MOO