The job exists, in the sense that Bob is currently doing it. Unless Bob turns in notice, your application will be in vain.
In larger organisations I think they'll usually be able to find work for an additional SuperBob. Perhaps not in smaller organisations, but I'd also expect them to be less likely to put up spurious vacancies.
In larger organisations I think they'll usually be able to find work for an additional SuperBob. Perhaps not in smaller organisations, but I'd also expect them to be less likely to put up spurious vacancies.