Just re-watched Catch-22 from Season 3 and it got me wondering if Jacob has visited Desmond. Desmond is explaining that he became a monk after he woke up in the gutter to a man asking him "Can I help you, brother?" Maybe this was Jacob touching him? He goes on to say he realized he had to sacrifice everything precious to him to answer a greater calling. But he got fired by the monks and went on to meet Penny, and you know the rest. Perhaps the island hasn't seen the last of him yet.