is never the case; have never heard of ~
Expresses that something has never happened or is never the case, often with a sense of disbelief or criticism.
This pattern is used to say that something has never occurred, often implying that it is unlikely to occur in the future as well. It often carries a nuance of skepticism or mild criticism about a person's behavior or a situation. For example, if someone always forgets to reply, you might say they have never once replied on time. The phrase is somewhat formal and is more common in written or careful speech, not in casual conversation.