The answer to that depends on exactly how one defines writing. If by writing we mean full alphabets, etc., then no, but that is not the critical function that the word played in what I wrote. If by writing we mean encoding structured mathematical information physically (which today consists not just of written words/sentences, but also non-linguistic equations and computer programs) so that it can be accurately and unambiguously digested (and modified or corrected by) others, then yes: as far as we know there was no mathematical knowledge outside of spoken and bodily counting or the most basic visual symmetries of objects like stones or sticks.

I was replying to your original post, which said nothing about mathematics. Rather it was about knowledge: "There is no such thing as knowledge that has never even been written down a single time by anyone or anything." And there's no evidence one way or the other about pre-writing math knowledge.

And of course Chinese is not written alphabetically, although I'm not clear what your point is about "full alphabets." (Technically, Arabic is not written with an alphabet either, but rather with an abjad--and the Arabs invented algebra. Similarly for most other languages written with Arabic script. But I won't argue that point, which I admit is rather esoteric.)