Welcome to Flyertalk. I would first go back and research the booking transaction. Where did the email response that had the booking details come from? If possible, go back to your browser history and confirm what site you were accessing on the day/time of booking. I find when I search for a site (like Ryanair), the first result is not necessarily the Ryanair website.

Doing something like the above will at least give you more evidence that Ryanair is wrong, or possibly let you know who to seek a refund from.