Having been switched from the Cutline to Coraline theme, I had experienced the problem of most of my sidebar widgets disappearing. They were not in the inactive widgets pane, either.
Lo and behold, I log on today, and there they are! They have all come back to the inactive widgets pane. I dragged everything back to the sidebar (I'm using the Vigilance theme for now) so my blog is back to the way it was. What a relief. Thanks, guys!