Can't play offline with new (2.0) launcher

When online, I can press "PLAY" button to launch Minecraft normally but when I launch Minecraft in offline, it will say some games files are missing, even I have downloaded it when online.
This is an example: http://www.minecraftforum.net/forums/support/modded-client-support/2795299-new-minecraft-launcher-will-not-play-offline