When people complain that an OC (or even other people) have treated them shabbily, I think they should consider how a similar situation would have been handled in the public arena:
What if your bike was tethered too close to a fire hydrant in the street? Do you think the authorities would wait until you had been contacted before removing your bike? Do you think you would escape a fine? And if there actually had been a fire emergency and the bike’s position delayed the fire brigade by even a minute, do you think the affected people or the public in general would have been sympathetic towards you? Ignorance is never an excuse.
I think you’re lucky not to be fined. I think you should also apologise to the OC.