I hear what your saying, taken individually you'd think a "lost art" would literally be an art no one remembers how to do. But like a lot of compound words and phrases in English, its actual meaning as used is different. In my experience, its pretty much always used in the sense of the article.

(SNL had a whole bit on this back in the 90's: "a chickpea is neither a chick nor a pea, discuss")