I'm currently playing Pokémon HG/SS with a Pokéwalker. One day I was transferring my Pokémon from the Pokéwalker back into the game and maybe like a couple of minutes later a Pokémon appeared. In this case, it was a Geodude, and it joined like I'd captured it, which I hadn't, and it's still here, on my Pokéwalker, is this normal?
Edit: I didn't have any Pokémon, item or anything else on the Pokéwalker when this one appeared.