Opt-out link in a message that redirects to a new survey

Hi everyone! I have a survey and in the distribution message I put the Opt-out link. But as we want to know the reason for the opt-out decision, that opt-out link redirects to another survey asking the reason (through a HTML line that calls the opt-out survey with its survey ID). In that new opt-out survey, I created a contact list trigger that unsubscribe that member from the list when any of the options of that question is shown. First time that worked so well, but when we changed the contact list for a real one (The test were with a fake contact list), this didn't worked that well. When the respondent send the answer for the opt-out survey, what happens is that a new contact is created in the selected contact list but without information in any field, and effectively with the status as "opted-out". Also, the person who asked to opt-out, continue with opted-in in status. I think this happens because the HTML line that redirects to the opt-out survey is not capturing the contact Email and for that, it creates a new contact to have something to change the status How can I link the contact information with the opt-out survey link?