I think the demon would show up to work the next day, go to his new cubicle and introduce himself as Phil the new graphic designer or whatever job he had just taken. The people in the office would accept it ("It's true, we do have graphics designers!") while those in competing firms might be a little confused they didn't see a job posting looking for a new graphic designer ("That's funny, I would have applied for that job if I saw the posting.") That's fine for a cog in the machine, but if you take the job of an important CEO the rest of the world might start to wonder how...