Wasn't there sposed to be a note from the Dark Brotherhood in Skyrim that said we know? Having got the game release day, and played it ever since, i've never gotten said note.

If you're on PC, start the E3 demo quest. You can get to it through console commands

I've gotten it before, I think.

I've gotten it as well, usually you just go without sleeping until a courier gives it to you.

Yeah i got it once or twice.

During manslaughter.