If you recall, George and Zoey split soon after the events of the arc that led to the time jump. John and George had been adjusting to the new status quo of George's dezombification and what that meant for them as friends and roomies... then Lyn comes into the picture. There was a throw away line about George and Jack's friendship being on the rocks right after George got receased... so while it's still not been shown what happened with that, that is the reason George didn't know Lyn was back in town.