Just turn up at the Desk with your passport. Most times when I check in with Ryanair they dont even look at your confirmation...they check your name on their computer and your flying..............
Worst that can happen is you get a snotty one at check in who will ask you to go to the Ryanair sales desk and get the booking reference number. It's only happened to me once in about 100 flights. Usually as previous poster says you just hand them your ID.
While waiting to check in on a ryanair flight recently the
person in front turned up without the confirmation email and they
were charged, didn't hear how much.