Sazed doesn't like Hemalurgy, don't think he's going to want anybody using it.
Also, I suspect that the few living people as of the end of HoA that have even a vague idea about it aren't going to want to talk about it, it's probable that nobody's going to know about it after they die.
Although I have an image of a bullet ending up as a accidental spike, by going through one person and hitting another. Mind you, that would take an insane amount of luck to create a useful spike.