[Cal578]

I don't think the lower left pin (in the Rick Astley photo) is a tack, nor is it photoshopped. It's a push pin, just like the upper left, but aimed straight at the camera so we don't see any of the side. The vague shadow below is because the light source is above.

So, I think that's a red herring. Let's focus on the rest of the hint(s).

I still haven't seen a really satisfactory explanation of "A dinner, missed".