I once only woke up (9.30am) because my son's headteacher rang to ask if everything was OK (cos we're never late)
I was mortified, especially as I teach at a nearby school and had to ring up and explain to them that I had only just woken up!
Either alarm clock hadn't gone off, or I had fallen asleep after my bath without setting it the night before (possible) or I'd slept through the alarm (also possible).
What made it worse was that I was supposed to be teaching my son's school receptionist's niece at the time when I eventually dropped my son off! And she knew that! But wasn't arsey...she's lovely, actually.
I was (and still am) mortified. I feel sorry for you, OP, cos I think you're pissed off because you know it's bad and resent someone else pointing it out - I would have felt exactly the same, so YANBU.