I had the good sense to check how things actually worked when I got home
Sounds like you fit both the criteria for "Smart and get things done".
I like programming with combinators -> They simply avoid the problem in the first place, so not knowing is irrelevant.
I think that a general awareness of the tools available to you is extremely useful. Specific knowledge isn't unless you're using them. Given that your friends "read about it today", I assume they don't often make use of this particular language feature - in which case it's fine not to know. In your case, not knowing was dangerous, and when you realised the limitations of your knowledge (unknown unknowns and all that), you corrected it.
My point is that I think all of this is covered in Joel's original essay, so your title isn't really justified.
Finally, I think there's a good essay to be written with a similar title, where you explore the point that "sometimes you need an expert". luu touches on this wrt hardware engineers: http://news.ycombinator.com/item?id=4882560
Sounds like you fit both the criteria for "Smart and get things done".
I like programming with combinators -> They simply avoid the problem in the first place, so not knowing is irrelevant.
I think that a general awareness of the tools available to you is extremely useful. Specific knowledge isn't unless you're using them. Given that your friends "read about it today", I assume they don't often make use of this particular language feature - in which case it's fine not to know. In your case, not knowing was dangerous, and when you realised the limitations of your knowledge (unknown unknowns and all that), you corrected it.
My point is that I think all of this is covered in Joel's original essay, so your title isn't really justified.
Finally, I think there's a good essay to be written with a similar title, where you explore the point that "sometimes you need an expert". luu touches on this wrt hardware engineers: http://news.ycombinator.com/item?id=4882560