I wonder what happens if you paid 300 in cash and 299 on amex? that's what I did...
Buyer's Protection Plan will only apply if you used the card for the entire cost of the item. All of their membership rewards work like that, including Traveler's Insurance. Say you're in Geneva, and decide to take a helicopter tour of the Alps. As you walk toward the helicopter, the tail rotor springs to life and lops off your arm. Unless you paid for the entire tour with your card, you're screwed.