sidebar suddenly disappear

i was almost done with my website and was just reading the code in the network admin-> themes-> editor template files when for some reasons, my computer went off. i powered it back on and now, i can no longer find the side bar on my website. the appearance-> -> customize-> widget panel displays the message “There are no widget areas currently rendered in the preview. Navigate in the preview to a template that makes use of a widget area in order to access its widgets here.” what do i do please?