I feel like there's a lot of stuff being said that's being taken very literally (by LE, the media, followers), but may actually just be poorly worded. Or even designed to sound like one thing, but really mean something else.
So, when it's said that his parents haven't seen him since Tuesday... did they really "see" him? Or did he come home with the van, and leave at some point before then, but has just been in contact with his parents in other ways, and Tuesday was the last contact they had with him? He could have split late last week, for all we know, once Gabby's family started reaching out to him/his parents, and perhaps he realized things were about to blow up.
Additionally, with the backpack, the statement is that he was last seen with a hiking backpack... But was he actually seen with it? Or did his parents know that he had a big hiking backpack when he came home, and realized that backpack is missing along with him, and the assumption is that he has it?