I can't delete songs from a playlist on my iPod?

So today my finger slipped while I was holding my iPod Touch and I accidentally added all the music on it to a playlist, as I discovered after pressing “Shuffle” and noticing there were several hundred more songs on the playlist than there were before, so I figured the only way for me to undo that mistake would be to manually delete all the unwanted music. The problem is, for some reason all the songs that weren’t originally in this playlist only show up when the playlist is playing—they don’t actually appear in the list on my iPod (which looks the same as it did before), nor when it’s connected to iTunes (ditto). So I seem to have no way to actually control or access or edit any of these new songs, as they seem to reside exclusively in this isolation bubble in the playlist they were unwittingly sent to. Can anyone help me crack this?