It doesn't look like they notify you.  If you are verified a winner, it looks like your prize will just show up.

BONUS INSTANT-WIN PRIZE WINNERS: 15 letters is an independent judging organization whose decisions as to the administration and operation of the Instant Win Game and the selection of potential winners are final and binding in all matters. There will be one hundred and seventy (170) random, computer-generated winning times during the Promotion Period, roughly three (3) random computer generated winning times per day. Once deemed a bonus instant-win prize winner via a pop-up notification by 15 letters, bonus instant-win prize winner will be asked to verify registration information. Bonus instant-win prizes will be fulfilled within 4 -6 weeks after winner has been confirmed. If necessary, bonus instant-win prize winner may be contacted by phone at the discretion of the Sponsor regarding appropriate size for prize won. Award of prize and confirmation of winner is contingent upon potential winner's qualification and compliance with Official Rules. Except where prohibited, acceptance of a bonus instant-win prize constitutes winner's consent that their name, likeness, voice and/or biographical data may be used in any medium for advertising and promotional purposes without limitation and without additional notice, compensation or consent. If any potential winner cannot be contacted or if prize is returned as undeliverable, potential winner forfeits prize.