That worked! You’re a brilliant genius, thanks so much!
I know for sure stylesheet.css and probably the header, too.
‘twentytwelve’ and ‘twentytwelve child theme’ are both folders in /themes, if that’s what you’re asking. my child theme is a copy of the whole parent theme, because I had made all of my customizations to the parent theme! When I switch back to the twentytwelve theme, though, everything reverts back to normal. Thank you so much for helping, I’ve wasted 2 hours confused and want to pull all my hair out!