Someone on the CNN website commenting on the show had an interesting thought:
Lori really is still alive at this point. They kind of gave it away on the after show called "The Talking Dead". After a cast member is killed off and is permanently off the series, they give them a cast party. They have for each of the major cast members killed off. They did for T-Dog but not for Lori. Those that say Carol rescues her are probably correct. Or both may show up on the Season Finale as walkers. Either way, both characters and actors are still officially part of the series (Lori and Carol).