I'm having a hard time following your thoughts here. She could have parked the car out front, not used the garage. The hubby said he talked to her from the top of the stairs. I assume he may have heard her and the daughter come in the front door... or perhaps there is a door into the kitchen from the garage which is visible from the upstairs landing. I don't see what difference it makes as far as where she was when they spoke.
The car was not found at the end of the driveway, it was on the side of the highway about a 1/2 mile from the house. LE said it appeared she had made a U-turn to park on the other side of the road, pointed in the direction of the house. Maybe she realized the tire was going flat and intended to drive back home, but it went completely flat before she could make it. And perhaps some sicko came along about that time and saw a stranded woman and took advantage of the opportunity. Makes as much sense as the husband staging the whole thing. Women have been abducted from their driveways or mailbox or jogging just a few yards from their house.
Another thing that has been discussed. People do occasionally run out of medicinal supplies. Perhaps the child came down with a sudden 24-hour virus, vomiting and diarrhea and there was no Kaopectate or Immodium handy. Most mothers would not think twice about making a quick run to a convenience store to get medicine, even in the middle of the night. Heck, we've made a run to get coffee when we ran out, just so we could have it first thing in the morning!
Someone else mentioned that the mom and sick daughter went to bed downstairs and the little sister was in her room upstairs. The brother said that his 9 y.o. sister remembered her mom lying down with her and when she woke up her mom was gone and she was in bed with her little sister. Does it make sense to carry a sleeping 9 y.o. child UPSTAIRS??? Not to me!!
I've also only read that it was the 9 y.o. at the sleepover, not both girls. I believe this misconception that it was both was due to the thought that Mom would have been terrified to leave one daughter home alone with the dad, which I think is ludicrous. If she was so afraid of him, she wouldn't have still been living in the same house. Where are we getting the idea that he is violent? I've never seen that mentioned in any media report. Yes, some divorcing couples fight and a few end up dead, but it's not a given. Suspicious, maybe but not written in stone.