You have no right to be annoyed.
Most children will get chicken pox and it is better that they get it when they are young, as if you get it when you are an adult it is much much worse.
The school told you that someone had it 2 weeks ago so you are probably annoyed that the child was in the school whilst infectious and you assume that your child would have got it from them.
You also then say that you will be taking your child to the doctor to confirm the chicken pox, and you fail to see that by doing that you will also be exposing other children at the doctors to this chicken pox and even adults.
There is no need to be annoyed about something that is natural, children are not usually locked away until the chicken pox is confirmed, if at all.
There is no real reason to worry, and certainly no reason at all to be annoyed.