Orphaned Thank You Pages

Our site currently uses Jot Form to capture leads generated by the site. I am trying to set up google goal tracking by using the thank you page URL. Jotform has a thank you message that appears after the form has been submitted, but it does not have a unique URL. I do have the ability to redirect to a new page when the submit button is pressed. My fear is that creating a page on the site that has no link to it from the site is going to negativity effect SEO, because that page is orphaned. Maybe my fear is unwarranted, but just curious how other people might handle this.