As I noted here, I had a buddy get dumped somewhere way back on the trail.
I don't have anybody around right now to try and reproduce it, but all I can remember about the situation is testing if he'd be alright (he logs out, I move, he logs back in, he's in the same place).
I also had another hearthling jump in at another point (my guide to the new place), but that definitely isn't where he was dumped. At this point I'm not sure if he was just ejected at some arbitrary point, but I have a suspicion that maybe it placed him where he originally logged out.
EDIT:
It also seems possible that this is related to some of the weirdness of people not being able to log back in to boats that seems to crop up and befuddle loftar.