Ha ha, I just now remembered why I never use CT's "Document notes" (found under: Resources > Notepad > Document note).
I closed and opened CT, and my note is now gone. No idea why or how. Oh well, that'll teach me to stray very far from Evernote.
see also: https://cafetran.freshdesk.com/support/discussions/topics/6000050186 ("RFE×2: Document note: open automatically on restart + auto-save function?")
How to save a Document Note and what is the difference with New Document?
Don't you get the "Save changes in the document" dialog for the Document note when you exit CafeTran?
> How to save a Document Note and what is the difference with New Document?
They are a part of CT project and can be saved along with the project via Project > Save project.