My child is in his first year at school, I have volunteered at a couple of school events but I have neither ?

the time nor the inclination to join the clique of Mums that hang around the teacher every morning and home time, subsequently the teacher can barely raise a smile for me. Today my child told me he'd been sick at lunchtime and his jumper was inside, when I asked her for it she dismissed me like a schoolchild and said 'it's the first I've heard of it' and walked off. I am fuming but am not sure how to resolve this. I wouldn't want to say anything to her and have her 'take it out' on my child Any advice??