Did they maybe forgret that it was your b-day? If they did know that it was your birthday, then I would be mad also. But, I learned that fhs' family doesn't really care to remember.
My fhs' family doesn't care to remember when its my birthday and I am not going to announce it to them (I'm not one to remind people about it). That's okay, I'm the better person for remembering theirs and having a card or gift for them. In the end, I feel better about myself.