What is "lost art"? lost skill? What do you mean by "lost" here?
ex)Your word-processing program will spell-check items for you. However, spelling is not a completely lost art. There are words that are not in the spell checker's dictionary....
A hundred years ago the fishermen who lived along the Columbia River used to use sail boats. They could sail their boats with or against the wind. The fishermen who live along the river now do not know how to operate a sail boat - it is a lost art. "lost" here means that they do not know how to do something that others knew. In your sentence, the author is saying that people have the ability to understand if a word is spelled correctly or not - it is not a lost art - they can spell words correctly.