I came across this problem:

I activated the "artistic color selection" docker and locked it to the side bar
Once restarted the docker disappeared and now I cannot tick the box to make it visible

https://drive.google.com/file/d/0B2NPtz ... sp=sharing

Any clue?
Thank you

Reset your workspace and try again. Making it 'locked' prevents it from being called from the menu, but I have no idea where the docker went off to.