Let's face it - these things happen. And if they can't fix it, and they haven't got another seat to move you to, then what are they supposed to do? Turn the aircraft round?

Still... you were inconvenienced, and I'm sure that if you were to write to customer service about this they'd probably give you something - miles, a voucher, whatever (I even had a hamper once!). As it only requires a fairly brief simple letter I think it's probably worth the effort.