Honestly I think the only way he takes her van and drives it to Florida without her is she's no longer alive. However that happened is unknown, but I don't see any scenario in my own mind how she lets him have the van unless she is no longer around. She very obviously loved that van and spent a lot of time on it and owned it, so, no, he doesn't just get the van, IMO, unless the worst possible thing happened, and he was aware of it. I'm not saying he caused whatever happened, but taking the van was like closing the door on the whole trip and their relationship.
... *unless* she did come back with him and then disappeared afterwards. Still, then, how does he end up with the van.
IMO it makes no sense.