So what happened to poppys father's hammer?

A possibility, to be sure. However, we will not know until the full extent of her lore is released. I understand your position on the matter, as the death of an immediate family member is incredibly significant to an individual's development, and changing such a core aspect of her lore would be seriously frowned upon. The only reason I suspect the circumstances have changed is due to the fact Poppy's new lines give no inclination that she lost or father, or that she even has one. I understand the absence of evidence is not evidence of absence, but it strikes me as rather odd that such a terrible event goes unmentioned.

Unless Poppy hides her anguish incredibly well behind a facade of naivety and awkwardness.

Perhaps she is now an orphan, taken in by a Demacian family, which might explain her unflattering opinion of her own kind and the adoption of Demacian values.