OP here with an update - AMEX eventually reversed their decision and removed the charge due to it "clearly being fraud" (AMEX service reps words). So, in the end, they did the right thing - but only after multiple attempts to force them to. I wonder how many people would have just given up and swallow the loss, saying "well, it's only $100", but I'm sure thats what they are counting on, which is dissapointing