What you need to find is the official rulebook Errata/FAQ and the one dealing specifically with Daemons. Both are available on the GW website.Direct Link to all the PDF-files
Now, for some reason GW has made it a bit tricky to find these.. This is what you need to do:
Go to the Main Page of the GW site.
Click on the "Gaming" category.
The last alternative in the dropdown menu is called Errata/FAQ articles, click here.
On the next page click on "Warhammer Frequently asked questions".
On the next page click on the green "Next" button.
Now you're home.
It's true that they forgot to enter alot of Daemonic Units into the main rulebook for some reason. Probably the biggest single blunder with the 8th Ed book actually.. So they are mentioned specifically in the Main Rulebook Errata.