Spellcraft can be used to identify a spell as it is being cast. Is there a roll to know of the existence of a spell? It seems like if you can identify a spell as it is being cast, you probably already know of the spell’s existence. Or, maybe not? Maybe you can identify what magics that the components being used to cast a spell would produce, so you don’t necessarily need to know of a spell’s existence to identify it being cast?
I also looked up Knowledge skills, but they do not discuss knowing of a spell’s existence. I would assume Arcana, Religion, and Nature could potentially be used to know of the existence of arcane, clerical/divine, and druidic/divine spells respectively. But, again, the DCs are not listed.
Obviously, the DM could adjudicate if this is not spelled out anywhere. And obviously, any spell whose existence a character did not know of, they could research. But, it is more the initial does my character know of a spell or not where I am wondering if there is a rule that describes this.