Preordering guaranteed you the deluxe edition, essentially; it would give you all those extras when the game unlocked if you preordered. You're experiencing a known issue: I had the extras before a recent hotfix was uploaded, and erased them from my extras page, both on Galaxy and my store library. I already sent a support ticket, others on the forum and Gamedec's discord are experiencing the same problem, the community manager suggested sending a support ticket to GOG, as it seems to be an issue on their end. Send a message to support, hopefully they'll sort this out.

EDIT: my items are back, other users are reporting the same, you should check your library’s extras again to see if your copy got updated :D