They didn't get loaded into your game by the server. Reload. Also submit a Support ticket as opposed to a BUG report, but it is to be covered in a incremental patch.

You may encounter some invisible NPCs during your play. This will be fixed in our next incremental patch, but in the meantime, completely closing the game and/or rebooting your system should make them appear.

see here: forums.elderscrollsonline.com/en/discussion/173858/esotu-console-launch-known-issues/p1

See this comprehensive thread my friend >>http://forums.elderscrollsonline.com/en/discussion/174296/invisible-and-non-interactive-npcs#latest