I would recommend just using your libsyn feed to submit with.
The current feed you are using is not validating
There are multiple error messages.
Not sure what you are using to create the feed - but it is causing issues.
Again - just put in the title and description in your libsyn account and then use your libsyn feed.
But you do need to publish those episode in your libsyn account and also put in the info to your libsyn account.
email me - rob at libsyn dot com if you have more questions on getting your libsyn feed set up.
The fact that your Store page has a web page indicates that the podcast has been accepted and should be in the Store in iTunes, so it seems most likely that there is a server problem going on. Your episode plays OK in the Store page. The feed can be subscribed to manually in iTunes and the episode plays OK there.
There are some errors in the feed, but they are minor and wouldn't cause this mystery disappearance in the Store. You have specified a category which is not one of the ones listed for use in feeds at
Your enclosure tag reads
<enclosure url="http://traffic.libsyn.com/audiobooknerds/ABN001.mp3" length="54.30" type="mp3"/>
The length must be the file size in bytes. The type should be audio/mpeg. None of these would cause your podcast not to appear in the Store, though they should be corrected.