Removing an invisible plugin…

I’ve recently been trying to “widgetise” my blogs footer, it didn’t work out so I restored the backups of the files I’d edited and eventually things seemed to go back to normal, except for one thing…

I forgot to remove the widget I’d added to the footer to test out code I’d used (I’d added it via the admin widget area), and despite erasing all traces of the extra sidebar the widget still appears to be in use, and I’m unable to add it to my default sidebar.

Is there a way to rectify this?

Oh, and for the record, I’ve already tried deleting its entry inside the MySQL database using phpmyadmin, but it hasn’t made any difference…