In working through my last post I managed to leave a remnant in Central Admin of a removed Host Named Site Collection that was stored in the default HNSC Content database. After many attempts to repair in a more acceptable way, (DB Repairs, removing/adding content db, etc) I finally realized that the issue wasn't in my HNSC content db, but rather a leftover reference in the SharePoint_Config DB. Taking a page from the book-of-things-you-should-never-do-in-SharePoint, I found the reference in the SiteMap table and had to manually delete that row. I backed up the database first in anticipation of impending doom, but it seems to have done the trick.
I'm going to poke around the internet a little more, hoping there's a better way to clean this up or even some timer job or other process that takes care of this in the future, but if you know of the better way, please post it.