The idea behind subliminal messages, is that your subconscious picks up, and deciphers messages that your conscious doesn't. Then logically, it would work the way if you saw a message briefly out of the corner of your eye, or missed what someone said, because you weren't focusing your attention on him/her. My question is, do you think it would be possible to find out a message that you missed in waking life by asking dream characters (or dream guide) about it while lucid, since they are controlled by your subconscious?