Custom HTML on forms for returning visitors doesn't trigger anything

We have two different gated assets on a microsite--a white paper and an on-demand webinar. The forms are set up so that if someone submits for the WP, then if they return for the webinar, it's welcoming them back with custom HTML and a download button. If they click the download button for the webinar, it takes them to the thank you page where they click again to view the webinar. 

I'm seeing that the thank you email and alert gets sent for the first submission, but the second "submission" isn't really a submission because it's not the form, but something in place of it to welcome them back. Is there a way that I can trigger this second action without just doing a progressive form? Can I add the form's button somehow into the HTML to simulate a form submission? (It is a different button on their second visit.) Thanks!