Page that doesn't exist but still being found?

I had created a picture portfolio (inserted a gallery into a post), but I don’t know what happened to that page. Google is still finding it (Webmaster Tools are counting it as an unfound URL), but I can’t find it to delete it. It simply doesn’t exist anywhere in the dashboard.

I’m comfortable with digging into the database, if someone could point me in the right direction. I just don’t know where to start. I want to start over, as the post wasn’t something I wanted to begin with, but was experimenting.

It’s possible it could have been plugin related, and I deleted a whole bunch of plugins – but I really thought it was just a gallery in a post.