An interesting little case mentioned in today's local German paper. A couple very recently flying from Germany to Spain checked in at the point of origin where the Ryanair staff accidently tore the "boarding card" for the return leg in half, handed it back to passengers, said "it will be OK".
Two weeks later at Girona they tried to check in for their return to Germany. Ryanair refused to accept the two pieces as one "boarding card" and insisted on printing out a new one - for €40, more than the flight cost.
They protested they had the original card so should not have to pay again: and were told to write to Ryanair HQ in English. Usual FR prevarication and eventually they gave up trying to get their €40 back.
Disclaimer: we used to fly with FR a lot and liked their cheap prices. However now we have the TGV from Spain to London we take that. Costlier but far more luxurious.