As stated you can't. In the MWI picture, you are split into two one who has measured it x+, the other x-. Both must send it back to have it recohere, and they must at the same time erase their measurement of which way it went -- really anything that distinguishes those two branches. They can record the fact that they did measure it, as this is the same in the two branches.

A person obviously can't just "forget", and will at best leak information into the environment, encoded as correlations in the noise of heat. A (reversible) computer, on the other hand, works quite well for doing this.