There is supposed to be a reverse Sync of the On-The-Go Playlist from your iPod Classic to iTunes. I think there may have been a problem with this in the past, but since my Classic has now failed, I can no longer test the feature. Other iPod models work differently to the Classic in this respect.
However, if I recall correctly from memory, on-the-go playlists will appear in on your Classic until you Sync the iPod with iTunes, as one of two names:
- On-The-Go (for an unsaved on-the-go playlist)
- Saved Playlist X (a saved On-The-Go Playlist, where X is is next unused number up)
When iTunes finds those Playlists at the Sync, it:
- renames them as On-The-Go X, where x is the next number in the sequence
- puts them onto you iPod Classic with the new name (providing all Playlist are set to Sync with the Classic)
So first of all, look for the Playlists in you iTunes Library. If you can find them, look to see if they are back on the iPod under the revised name.
If not, you may have to rebuild them after all.