If you received the Grill Guru as an incentive from e.g. your employer or won it in a competition or the like, then you can enclose a document (letter or e-mail) as proof of warranty which shows that you received or won the Grill Guru. Items that are required to be listed here are: name of giver, name of receiver (owner), what type of model and the date of purchase. This then serves as proof of purchase.
If you have received the Grill Guru as a gift, we still recommend that you ask the giver for proof of purchase, as uncomfortable as that can sometimes be.