>저는 제품을 만드는 사람이고 제품을 홍보하는 측은 따로 있는지라..
>저는 구지 행사장에 나갈 필요가 없었지만, 나름데로 눈요기도 해볼겸..
>혹시나 도울일이 있으면 도울겸..해서 뒤따라 가게되었지요.
This suggest that there was somebody else who took in charge of this event from hyour company. If that’s the case, you could appeal through your manager or HR. I don’t think it is any good to accept any such warning without complaining unless it was clearly your responsibility to deal with the matters in the event. You may feel like you should have done better, but that’s a different matter. Even if they don’t take the earing notice back, I think it makes difference if you try.

In any case, according to this short explanation, I don’t think it’s your responsibility. So, let’s cheer up. Today is today and tomorrow is tomorrow!