Strange indication to a missing UV-Map? Good day. 

For some reason I see a strange purple reflection in my scene. I know that this is usually an indication to a missing UV-Map. But I unwrapped every object in my scene. The background is transparent with an image added in the compositor.

Do you guys have some ideas where this might come from?
As written in the comments - I'm just getting old. 

Gone is the purple reflection:



[edit]
Sorry for the missing details. I forgot that I wanted to use a world background image at the beginning. Therefore I changed the surface type to "image" without actually asigning one. That caused the reflections.