Is there an equivalent of 'lost in translation' but for writing? As in all the subtle information we lose when texting instead of talking face to face
Solution 1:
"Translation" is applicable to written words as well as spoken words. There is no reason not to use "Lost in translation" when writing.
If you are talking about the information you lose when communicating in writing rather than face to face, that is called "non-verbal information", also called "non-verbal cues", "non verbal context" etc.
"When communicating in writing, we lack the non-verbal information that provides additional understanding and context".