1 in a million... or worse... yeah... a lot worse odds than that. Googling for how many have ever been found... can't find it...
IMO No chance. Here's an article I feel has no credibility: https://coinsite.com/1965-kennedy-half-minted-in-90-percent-silver/
That guy saying he has one means nothing. Obviously he hasn't had it authenticated because if he had, the news of such a rare coin would be everywhere. As I said before : "Lots of talk about them , Edward. None have ever been authenticated."
I can't count the number of times that someone has came to a coin forum and said they have one. I wish someone would find one but don't feel it will ever happen. I could see it being a four figure coin.
There are some things that are just mythical. 1964 Peace dollar (oh there's one hidden in LBJ's library, a gift from the mint director. A descendant of the mint director also has one.) Now in this case, since examples of the 1965 dime and quarter exist on 90% planchets, it is possible for the 1965 half to exist. But after 54 years one example has not surfaced. So until it does, it is the Bigfoot coin. Reading other posts, someone has claimed to pay $7,000 for one. But where is this coin? It would fetch 10-100 times that price.