Does divorce occur by saying "Ma'a as-salamah" (goodbye) with the intention of divorce, without the wife's awareness or any indication to her?

As long as you did not utter a clear divorce, nor did you intend to effect it through an implicit statement, then it has not occurred. One must be wary of obsessive doubts concerning matters of divorce or anything else, as they are a great source of evil, and turning away from them is the best remedy.