About every month, I take out all my credit card receipts from my wallet and compare them to my bank statements. it's not that I am an accounting maniac, or that I need to control my expenses tightly, but you never know.
Hence, moments ago I noticed my American Express statement stated that I paid $167.68 for a quick bite with a friend in Napa earlier this month (the second number is euros).

huh? for 2 dishes. I checked through my credit card slips, and there it was: I had actually paid $100 less, including tip.

The food at Bouchon (Yountville) was nice, the setting enjoyable, and the people there pleasant. So my guess is that this is just a mistake, but you never know.
I called American Express, and sent them a copy of the receipts above. I should get a refund in 10 days more or less.
So payment also has its issues in the offline world, with reputable merchants. Be cautious.