That topic is only for Divine Divinity.
You can check out the
Save Game Editor topic. There is an item editor, but I don't know if it can add missing quest items, as well as a save editor (don't know if you can search yet, but if you can find the item listed you may be able to get its coordinates).
Other than that, you can email supportdos@larian.com, with a description of the problem and the report.zip file generated by the
D:OS support tool (for the PC version). The report will contain system and game information, any crash dumps, and your saved games. If file size is an issue, you can delete all saves from the zip except your latest save, and (if available) the most recent save where you have the note and the oldest where it is missing (especially if those saves are relatively close together and you remember what you did between those points).
