Anonymous wrote:your kid needs to handle it first
This. This happened to my son last year. He emailed the teacher and said something along the lines of "hi Mrs X. I noticed I was marked absent in class yesterday. I was there. I sat in the back next to Morgan.".
Teacher emailed back basically saying maybe they missed him or didn't hear him or just marked it wrong but it was fixed.
I'm sure a one time thing, they don't put up a fight. If the kid tries to use the "you marked me absent by mistake" repeatedly, I'm sure it would be a different story.
But this is a perfect thing for your kid to handle on his own and if it doesn't get resolved, then you can step in.