I just recently restarted Yellow and got up to the first cave. So I turned it off and played my Xbox. When I turned it on again a little later, half of my Pokémon were gone! I said a few naughty words, thinking it was some sort of glitch. So I started a brand new game, finally reaching the cave entrance once more. I turned it off again, and went to baseball practice for a couple of hours. I got back, turned the game on....and my Pokémon were all gone! So I searched for my little brother, revenge burning in my eyes. He admitted his treachery as I...nicely...persuaded him.