I came across this question from a while back. I was surprised to see that it was closed.
Sure, OP made (and has acknowledged that it was) a very stupid mistake. But does that have anything to do with the question being closed? I wouldn't assume it, but I'm struggling to think of any other reason.
This question seems firmly on-topic to me. It's about job hunting, learning from mistakes, the application process, interviews, etc. And OP managed to elicit some excellent answers.
What makes this question off-topic?