EC paid ad got on my blog somehow

I had to remove the "No Paid EC Ads" title above my EC card because I found a paid ad being displayed on my blog. I know I rejected all paid ads but somehow the paid ad was up on my widget. I don't know if it was an error, but I will keep an eye out from now on to make sure that my advertisers get 100% of the page views when they advertise on my blog.