Regarding the "missing" Spock's Brain cue just after "there is no mind" - it really looks like it was editorially created. It reuses the sting from "Poor Spock" and then segues into "Spock Walks." There's an overlay in there apparently, but there isn't a missing cue. It may have been reused in later episodes because they felt it sounded good and kept the edit for later use. Stranger things have happened.