Had he been right in his fear that Johnny had not been unconscious back in Tubacca, that he had caught Anse's greeting?
His fear that Johnny had been conscious in Tubacca was great. 
mnli hypothesis: His fear that Johnny had been conscious in Tubacca was great.  premise: Had he been right in his fear that Johnny had not been unconscious back in Tubacca, that he had caught Anse's greeting?