Mark,
There's actually a good chance that it is published. The iTunes store can take 1-3 (? this is a guess) days to show that a new episode is there.
Assuming the episode is showing up in your RSS feed, there are a couple of ways to tell:
1. If you're subscribed to the podcast, go to your own app and see if the episode is there.
2. Are you on other platforms like Stitcher? If the episode is there, then there's nothing wrong with your feed. It will show up in iTunes eventually. But, again, people who are already subscribed will already have the new episode.
Hope that helps.
Sarah