Hi Steve,
When a "Saved Listing" dissappears, my first check is to see if I'm using any Filters or other settings at the top of the Saved Listings page, that would hide the listing.
Is this the 1st listing you've created? If so, there are sometimes browser settings or other blocks that prevent some Auctiva pages from functioning. I'd try a quick test and see if Save is actually working on the one-page lister. Normally, save completes and you're taken out of the lister page to the main Listings tab page. If that's not happening, it may be the cause and save failed (not working).
Which OS and browser are you using, and have you checked the FAQs at HELP for cookie and other requirements for your browser?
Danno