I have a similar story. I saw a freaking Imp LAND. Basically, I was just as shocked as you were. It was about a week or two ago.
I still find new things in Oblivion even after 1000+ hours of gameplay. Not too long ago I found Lost Boy Cavern for the first time. All the time I hear a new line of dialogue that I've somehow never heard before. For example, just yesterday I talked to one of the guards in Leyawiin and he told me the story of Torval the Pilot, the High Elf who discovered the Niben, and the Patron saint of Leyawiin. He then informed me that the statue in the Southwest of Leyawiin was of Torval. I never knew.