I started using the plugin Theme Test Drive yesterday, in an attempt to play with another theme. All seemed good at first, until none of the changes showed up unless I logged out of WP, and logged in again.
Anyway, I decided that was ridiculous, so I simply activated the new theme (Responsive) and tinker with it live.
When I activated the theme, I was told that my plugins would be restored should I switch back. That didn't happen. I switched back to see my sight without any plugins, sidebars, and things were just a flat out mess.
I went back to the theme page to see that my Parent theme (Hybrid... I'm using Hybrid News as a Child) was gone. It showed up in my FTP, but not on the page.
I deleted the Parent theme in my FTP in order to reload it. That seemed to work, only when I clicked on the theme, Responsive showed up as the active theme, only my site still shows the beat up Hybrid News... AND I can't switch to any theme at all!
I cleared my cache and cookies btw...