unable to locate page in WP

I am having real difficulty locating this page http://www.jigsawbox.com/webinar/cancelSub/jigsawbox-form.php in my wordpress site.

When I look at the page source info, it tells me the title of the page is ‘JigsawBox Advantage Thank You’ (which doesn’t make sense as this is not what the page is) and when I look at all the pages in WP with this title, none of them are this page.

Help!