I recently tried to download an episode of a podcast on my iPhone, but the download failed. Nevertheless, the podcast was listed on my iPhone, with one episode, but trying to play that episode did nothing. There was no way to delete it. When I deleted it from within the Podcasts app, it seemed to go away, but when I deleted the Podcasts app to use the Music app for listening to Podcasts, it was still there.
I tried turning off syncing of podcasts in iTunes, syncing, then turning it back on, but it was still there. There was no obvious way to delete this "phantom" podcast.
I finally tried going into Settings > General > Usage > Music, and saw the podcast listed in the Podcasts list. A swipe to the right on its name, a tap on the Delete button, and it was finally gone.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20121008000645629