Dragging the raw files to iTunes won't make them show up in the Podcasts section since it won't know to tie them to the specific feed that they'd be from. They may be in your general Music Library as regular tracks. Check there first. For any new episodes you'd need to resubscribe to the particular podcast, assuming they've become unsubscribed as well.
Have you tried the apple support pages? That would be the best place, since they make the thing.
