How does this happen?

Can anyone please tell me how this child goes to bed unscathed and wakes up with this?

I mean, honestly! That is long and deep! And it's gonna leave a mark!

And when I ask him what happened, he says he doesn't know, and then he says he doesn't want to talk about it?

I'd think if I got a gash like this overnight, I would probably wake up and let someone know.

Oh child, you are a mystery to me.

Thank you for keeping it interesting.