I've been learning my way around wordpress by building my own child-theme of Thematic. Everything had been working for a while... I went to change the template used by some of the pages (which I had success with in the past), but suddenly only "default template" was showing in the dropdown.
I figured out that this was because it had somehow reverted to the TwentyEleven theme, but worse than that: my own custom child-theme was no longer listed under "available themes." (I made absolutely no alterations to the file structure or the comments section of style.css; it is exactly the same as it was when everything was working fine.)
The SUPER strange part is that my site was still displaying as if my child-theme was active!! Seriously, WHY THE FACE?! o_0 (This also makes it impossible to know when the problem occurred.)
Unfortunately, I tried switching to Thematic, and seeing if that made my child-theme reappear as an option, which didn't work, so now my site looks like Thematic, and I can no longer continue working on other aspects of my custom style.css until this problem is resolved.
I tried creating a brand new child-theme, the same way I did it the first time (which had worked), and it also did not show up.
I cannot provide a link to my site because I'm building it locally, using MAMP.
Sure hope someone can help; thanks!