Viajero, It's terrible that you had to go through that unpleasant and unfortunate experience. We learnt the hard way as well, although in our case it was only on a domestic flight.

Apparently the prerequisite to have THE credit card used for purchase of an E-ticket started at the beginning of this year, and unfortunately the banner advising of this prerequisit is not very obvious and appears when your selected itinerary is displayed on Iberia.com. It's abanner using smallish font and an insipid yellow colour.

Hope you're able to sort this out.