You're supposed to have the rubber duck ask these questions too.

The difference here was that I was actually writing a letter / forum post that other people could have seen. I was doing this with the urgency of 'If there's an obvious solution to this, I'm going to look like a moron'. In contrast, a rubber duck, well... it's just me.

I think the distinction you drew in the other branch of this conversation is more important. Getting a little skin in the game of 'get this right now (or satisfy yourself that it's genuinely hard)'.