The belief that the winning candidate had 10 coins in his pocket--expressed exactly that way--did turn out to be true, though. It is just that the winning candidate wasn't Jones but Smith.

It's like saying "The one who will get the job has black hair." Lots of people have black hair. And sometimes we are mistaken about people's hair color--they dye it, shave it, show us an old photograph, or we are introduced to the wrong person, or we don't notice their hair color to begin with, or we forget what they look like, etc. It might turn out to be true that the person who gets the job happens to have black hair.

For some reason, we'd had another candidate in mind, so in that sense, the belief was mistaken. Yet the original statement, exactly as it was expressed, turned out to be true.