Chemistry homework

Apparently, in the week before half term our chemistry teacher set us homework, which was due in on monday. I had no memory of this, it is not written in my homework journal and I did not have either of the two sheets. I explained all this to our teacher, but still she gave me a warning, and told me to 'look for [the sheets] at home'. This I did. I could not find them anywhere, so I went back to chemistry on Wednesday and told her so. Her responce? Another warning, and that I should have 'come and gotten the sheets off of [her] at the end of the lesson like everybody else'. WTF?