Can't remove custom sidebar widget

I’m trying to help a friend with his new blog, and I can’t seem to figure out what he did here.

He’s not too computer savvy so I offered help, but this is even stumping me. Basically he’s got a custom html sidebar widget that appears only on the blog posts. He wants to remove it, but doesn’t remember how he got it there in the first place.

I figured this would be easy enough, but I actually can’t find it. I’ve got full access to the site, so I’m looking everywhere, but I have no idea how this thing is appearing.

I assumed it was done using the text widget, but when I look in the widget list, it’s not included in the sidebar. I went in the editor and looked through the obvious php files, but found nothing. I couldn’t think of a better way, so I downloaded a backup of the whole site and used a file renaming utility to rename everything to txt files so that I could search the code within them. Still turned up nothing.

What the heck am I missing? Not sure what other info I could provide that might help.

Any ideas??