And, if this guy is not yours, you still have a DNA card, that you can play.
^^ This. The OP on the IGS does sort of cover for this situation with the DNA record thing. Just claim it's some guy pretending to be him to be an attention-whore, and that's more or less that.
Assuming that it's
not Ghost playing Sanshananigans with you guys, however, taking over someone else's NPC - godmoding them, really - is an
incredibly dick move. Doing shit like that without prior consent is unequivocably Doing It Wrong™, and whoever's doing it is probably not going to like the results when they get found out.
Given the size of our community it's only a matter of time anyway.