That information is kept in the wp_options with the option_name
of “widget_text”. In fact all the text widgets keep their information in that same record.
Just guessing–did you have the old Sidebar Widget plugin ever installed? If so maybe it is left over from that.
AAhhhh… yes the old sidebar widget was deactivated and, of course, after upgrade it cannot be reactivated.
That must be it.
Thank you.
I can sleep tonight.
-P.
ps: just for fun I might restore old version on another server from backup… a good test of backups, but otherwise pointless.