You didn’t do anything wrong, they were unfair with you, and the attitude of your co-worker saying “just make sure you don’t do it again” was humiliating, patronizing, unnecessary, unconstructive, and showing an absolute lack of humanity and sympathy. You are right to feel angry, and a subject of unfairness.
HOWEVER my advice is this: don’t stick to the (appropriate) feeling of anger because it will not do you any good. Also remember that even though this whole situation is unfair to you, from a strict legalist point-of-view it may very well be that you don’t have the law on your side. So, my second advice is to remember that in adult life (perhaps also in childhood) we have sometimes to swallow a bit of unfairness in order to be allowed to carry on with our lives, and jobs.
I am sorry to know about this situation, but it happens so many times to good people with ADD and good people without ADD. You supposedly break some rule, and this is used against you sometimes in full extent, not because enforcing the rule was so important in the first place, but because breaking the rule gave to those ridiculous dictatores some extra power to exert on you, while “having the law” on their side.
Life goes one!