I worked on the starterkit project #9 motorized pinwheel, and the motor worked just fine.
I then tried to add a potentiometer, and now the motor won't rotate at all any more (neither in the current nor in the project's baseline configuration). I also tried connecting the motor to the 9V battery directly, to no avail.
I did check the battery by briefly connecting a LED right away. The motor apparently also still generates current if I turn it manually (checked with a directly connected LED either).
What else can I do to check what's wrong with the motor? Is it possible that I somehow accidently killed it with my attempts with the potentiometer?