Lead unsubscribed before receiving email - form completion only activity

We had a user group today where I distributed a link for a form for raffle entry.  I have a lead who was created today via the form and has never received any other communications from us.  However,he has unsubscribed checked.  His new lead record is the only appearance of his email address in either Marketo or Salesforce.  Unsubscribe is definitely nowhere in my flow and I'm completely confused.

Any ideas?