I like those shows. There were two mini-series about that last year and now a long series. I sometimes disagree with them, but it's interesting to see what would happen and how tenuous our existence is. Moreover, it reveals some potential problems that could happen relatively rapidly in the event of a breakdown in services even if people didn't disappear. I'm thinking of the NY subway flooding and the nuclear plant cooling pools drying up and spreading radioactive material across the countryside. Oddly enough, they mention that devestating calamity and then move on to some other aspect of animal life forgetting that they would likely be wiped out by the radiation they mentioned in another episode. In other words, they look at some aspects individually and with tunnel vision and ignore the wider world.
As for what would happen to those "left behind" if Group X suddenly disappeared, you might want to examine christian eschatological writings on the subject, such as the Left Behind series of books. Howeover, I don't think we can discuss it here.
Et tu BAUT? Quantum mutatus ab illo.