No one looks it over. No editor, no proofer involved in the process. Certainly, any spell-checker would not have caught this error in all likelihood.
Yet it stood out to me. I glossed over the article, idly perusing the New York Times while sitting at the table in my sister-in-law's house, and suddenly the running gait of my eyes tripped over a large obstacle. That's what spelling (even contextual spelling) errors do to me, usually. They stop me, they take me out of the reading process and a section of my brain lights up. It's the same section that believes in justice, I think, and maybe even seats the sense of a universal intelligence guiding us along, beyond the ken of mortal understanding. Because I believe in and work with these things, discrepancies and exceptions snag my attention as my conscious thought races past.
I dug out my Wacom tablet, selected an appropriately red color for my "ink," took electric pen in hand, and marked this up in nothing more or less ignominious than a recent version of MS Paint. Now that I know how to do that, and provided I always keep my camera on me, no homemade signage will be safe from my scrutiny.