Try making that argument when a bank makes a deposit error in your favor, you go ahead and spend the money, and they find the discrepancy later in an audit. Let me know how it goes.

T&Cs for MP say: "Alaska Airlines reserves the right to audit Mileage Plan accounts at any time and without notice to the member to ensure compliance with these Mileage Plan Conditions of Membership and applicable conditions of carriage and/or tariffs."