Uhm Yea that is called admin disrespect, and insulting an admin in server undermines their authority. Hence why we have it against the rules. Considering it was a random like you said and not someone like me, it could hardly be called playful. hence the ban (And if I pulled the same stunt, I'm sure she would ban me to if I didn't have admin currently)
Also as said in another thread, When a situation gets out of hand, you need to get it in hand as soon as possible. When something like that happens again, don't get associated. Its like when cops arrest someone, and you walk up to the cop, you get arrested to. We have a really good unban me and admin abuse section here if what the admin did was wrong.