That would mean God had to have invented a writing system for Adam to use, and to be frank that's, if not surpassing, at least bordering on the absurd. The earliest form of writing for which we have any evidence is cuneiform, which was invented by the Sumerians as a simplification of older pictographs and simple numeric notation. Other, independent writing systems developed elsewhere, such as in China and in Egypt largely following a similar pattern of pictographic proto-writing to writing proper. What we know today as the Hebrew abjad, for example, is actually the Aramaic script which was borrowed to write Hebrew in the post-exilic period. Prior to the adoption of the Aramaic script there did exist what is known as the Paleo-Hebrew script, a form of which is still in use today by the Samaritans. Paleo-Hebrew and Aramaic are both derived from the earlier Phoenician script, which is descended from Proto-Sinaitic, likely coming from Egyptian hieroglyphs, a comparison between the Egyptian hieroglyph for "ox", and Proto-Sinaitic aleph, along with Phoenician, Paleo-Hebrew, and Aramaic aleph show the development of a pictographic representation of "ox" being borrowed to use as a morpheme in an proper writing system. Which in turn gave rise to the Greek alpha, and Latin 'A'.
"That would mean God had to have invented a writing system for Adam to use, and to be frank that's, if not surpassing, at least bordering on the absurd."
So a God that when he speaks everything came into existence does not have the power to give Adam the ability to write? How is that absurd? He gave Adam thought, speech, consciousness, the ability to reason and make decisions, think, act, full emotions, ad infinitum. He was the pinnacle of mankind. But somehow God could not have given him this ability? Your logic is skewed. Just because there is no record of it, your evidence(or lack there of) does not mean it supersedes Gods ability's. "Nothing is impossible for God" When God created Adam he was complete so why would him having the ability to write seem so absurd?