More likely, no one cared enough to make the effort to become fluent in the language. I would say that if it can be categorized as a language, it can be learne

More likely, no one cared enough to make the effort to become fluent in the language. I would say that if it can be categorized as a language, it can be learned, because categorization would require the observation of patterns of cause and effect. (I know they're illusions, but they're useful illusions.) Then it's just a matter of gathering data, developing hypotheses, and testing your interpretation of the data by asking someone if their hovercraft is full of eels.