lsoucy

Well, to close out this topic – my original problem was resolved with Esmi’s recommendation to rename the active theme via ftp in order to temporarily disable it. This gained me access to the dashboard again, from which I was able to re-activate my theme. Still not sure why it “broke” in the first place.
My secondary issue of losing all my text widgets in the process, however, was only resolved by recreating them from scratch.

So there’s no general work-around to restore text widgets that are still stored in the WordPress database? For what it’s worth, they don’t even show as Inactive Widgets when I switch to the Twentyfourteen theme.

I’m using the Rescue theme downloaded from Themeforest.

Yes but unfortunately they’re not listed there.

Thanks Esmi! Renaming the theme folder got the dashboard back. I was then able to re-activate my original theme. Now all of my widgets are gone, which I understand can happen when switching themes. However, they’re not even displayed in the dashboard as Inactive, though I can see them in the database (Options table). How can I restore my widgets?