I personally thought Lori was a bit too big to be eaten completely whole by the one zombie alone without some sort of bone or cartage left behind. Then again, it did have some time to eat her all the way, didn't it (but zombies don't eat the bones, do they?)...? It certainly seemed like Rick took his time getting to the room she was left in, so who knows. I do admit, it's still odd. However, I think that's more of a production error, than a 'omg, Lori is still alive' thing. I honestly don't think she is, and I am okay with that. Putting aside my dislike for her, it would have ruined the moment, the suspense, the sheer heartbreaking moments in that episode, if she were to just show up later all like 'oh hai guys, I survived the blood loss and didn't get eaten, even though I was weak, cut open, weaponless and pretty much welcoming death. Lol".