Got a message from the school that they are backlogged in processing absences from today. I imagine their classes were awfully sparse today.
You should have told them that you personally dropped the kids off this morning and how dare they only call you now? If something happens you will hold them fully responsible.
LALTS
And if the homeroom teacher messes up, or there's a sub who doesn't know everyone, they can be marked as absent even though they're there. Got that call several times last year, and I'd have to call and tell them, in fact, my child IS there, then wait while they confirm it.