@א-ש if your database is damaged, then immediate retrieval won't be possible. Do you at least have a backup of the database ? From the comment below around accepting the loss of posts and users, it doesn't seem to be the case.
What I always do is take a copy of the CSS and keep it up to date in a text file outside of NodeBB.
@phenomlab Good to know. Thx for the report. I need to get updated to the latest and greatest. One of these days... meanwhile... the ol' "if it ain't broke don't fix it" adage seems to be serving me reasonably well! 👍