I think they covered it multiple times. Are there actually casual viewers of Lost? I thought it was pretty much an all or nothing proposition. I only know people who either watched it or didn't watch it.

What they didn't cover in any significant detail (among other things) is why that particular baby was stolen. I can't even recall for certain wether they showed the kidnapping in an episode. Do you remember?

The kidnapping can be easily explained away as being done to protect the child, knowing that the mother was either going mad or soon to also be killed by the smoke monster. But that's sort of an afterthought.

The whole handling of "the others" was a little inconsistent and probably comes down to the way their involvement in the storyline evolved and wasn't carved out in stone ahead of time.