OK, I asked my french friend about this for some examples and it seems that it is used to stress the fact that the expectation in the first part of the sentence was not met (which isn't to say the first part of the sentence was untrue). The reason it is awkward to translate into English is because we would use an appropriate auxillary verb. For example: He thought he would win but he DIDN'T or I thought he was clever but actually he ISN'T. "And yet no" I suppose would be intelligible but just sounds really weird.
Seems like a random arrangement of words to me without any context go go on.
Laurie above is correct. To explain the concept a little further:
not yet = yet refers to time yet no(t) = yet refers to circumstance
"Have you had breakfast?"
(As of this time, they have have not had breakfast)
"If you've been here for an hour, shouldn't they have delivered breakfast?" "And yet not" (Despite the circumstance, they have not delivered breakfast.)