I considered adding this trope to the list on The British Railway Stories. In episode 1 of that, when Allen is pulling a failed train, the coupling between him and the failed locomotive breaks and he ends up leaving it behind. However, this trope seems to mainly list examples where the car was deliberately uncouples from the train by people, so I'm not fully certain if the example counts.
I considered adding this trope to the list on The British Railway Stories. In episode 1 of that, when Allen is pulling a failed train, the coupling between him and the failed locomotive breaks and he ends up leaving it behind. However, this trope seems to mainly list examples where the car was deliberately uncouples from the train by people, so I'm not fully certain if the example counts.