I believe what you described (topic creator) is a psychological disorder called Depersonalization. The feeling that "you" are not in your body, or that your body is not yours. It makes the world seem like a screen or a painting put in front of your eyes, and makes your body feel and look like someone elses (which always caused me to feel like I was about to vanish or something). I got Depersonalization from a WICKED mushroom trip (level 5), and after it I would depersonalize heavily once a day (atleast) for the next few weeks.

If you havent had it happen again since you were on weed then dont worry about it. it might not even be depersonalization, and its rare that it will recurr in your sobreity (though thats what happened to me). It got to the point where it would happen to me so much that I just stopped letting it bother me (though it truly is a grotesque feeling), i still get it mildly when I get high as hell. The key is to not focus on it.