When you purchased directly from lifeproof.com, you created an online record of your order. If you checked out while signed into your account, you can find your order number in the "order history" section of your account. The order number can also be referenced in your confirmation email.
*LifeProof is not responsible for return shipping charges. For customers who purchase and return their product within the United States, LifeProof provides a courtesy shipping label for $5 USD.