I’m getting the vibes that they went somewhere deep and he left her there. He tried to leave her before with the van, but was unsuccessful. This time he lured her into the wilderness and ditched her. Murder but not with his bare hands.
That’s why he didn’t have any stuff he left it with her probably when she was sleeping.
If they were in the tent and he drove off intentionally, that would have to mean they were on a road of some sort. That van didn't have 4wd or high clearance, or a big engine so it would be an easily driveable road. Unless he beat her into unconsciousness, she would have been able to walk out and in 3 weeks someone would have found.. something.