Complain, by letter, to the owner of the establishment.
Be articulate, be polite, do not make threats, point out the issue and explain that you feel it must be a misunderstanding.
A number of years back myself and some friends were harrassed on the way in by bouncers pulling the 'regulars only' trick in a well known pub in Phibsboro, we were in fact regulars, the bouncers were new. They were rude, undignified, and basically treated us like children before deigning to allow us in.
I wrote and complained to the owner, not only did I receive a letter of apology and a 50 quid voucher for use in the establishment but he photocopied my letter and gave it to the security firm he used so that (in his words) 'the apes they employ can see themselves as others see them' and he also said that he would be using my letter of complaint as ammo in an upcoming meeting to tender for the security contract.
Complaint letters to the right people work. Particularly if you are polite and articulate.