This is a pretty common occurrence. Missing textures mostly happens because your computer fails to load something, not because the texture doesn't exist.
Try going back to the same location with lower graphic settings. If it's still happening, there may be a real issue but if it doesn't, it could simply be linked to your own computer's power. (Just guessing here, I don't know your specs.)

I'm afraid, I cannot recreate it. It occurred only in Castle of the Worm and I cannot go back there, because it was story line quest. I didn't observe missing textures in any other location that I've visited. Sorry.