I can confirm it DOES happen. I've just returned from a European river cruise. On day 4 when in Budapest I noticed 4 transactions on my Mastercard totaling just over $1,000. We hadn't used our Mastercard at all on the the tour, and the only feasible and reasonable explanation was someone had scanned the card while in my wife's wallet, which by the way contained other cards with RFIDs. The bank repaid the money, so no damage done, but we had to cancel the card and get a new one when we got back, which is a pain in the xx_x when you have lots of direct debits from the card, and it meant that we couldn't use our card on the tour (OK that was a blessing!!!!

).
No-one else on the cruise had this problem, so the chances are miniscule, but I know I will be buying the protective sleeves for our next trip.