The idea that if you supposedly went back in time to pick yourself up, and went back with yourself in the future, and something prevented you from going to the past (death, coma, etc), you would disappear from the time frame entirely, due to the fact that if you dissapeared in the past, you would dissapear in the future.
However, if you dissapeared in the future, you never would have been in the past to pick yourself up.
1. You're in the present.
2. You see yourself, and then you kidnap you.
3. you will dissapear from the time frame forever, probably because it's impossible to go back in time, or you are trapped in the future by death, coma, etc.
4. If you dissapear, then you're future self disappears, because you dissapear. However, you would never kidnap yourself if you dissapeared, and you would be back in the present, and you would kidnap yourself again. And again, and again...