I am not too familiar with forensic linguistics so I will agree and say that it is a lost art because I have not heard of it. If it is a good thing let us bring it back so everyone can enjoy this lost art. There has been way too many things that have been dropped by the wayside.
I do believe that forensic linguistics is a lost art today. In fact, I believe that most forms of linguistics are on the decline. In today's society, we no longer study the intricacies of language because so much of our communication is electronic and automated. I think this puts our students and professionals at a disadvantage.
I do believe that forensic linguistics is a dying skill set. It is a very specialized branch of knowledge that focuses on the use of language in legal texts as well as the examination of vocal patterns and writing style to prosecute the guilty and proceed with emergency calls. Unfortunately, though, it seems that nowadays people are more interested in the flashier, TV-style forensic sciences that involve the examination of cadavers.
Even though a field like forensic linguistics may seem to have little practical application, I believe it and similar academic fields should be offered as electives in university study. Even a subject with little practical application on its own can train the mind to think in new ways and provide stimulating and intellectual conversation pieces.