I am guessing but it may depend on whether the parents are ok with the child still associating or not. Also the child's attitude should be taken into account. Things may have changed since the child has seen and heard conversations between the parents leading up to the disfellowshipping, so may not want any more contact.
I knew of a case where this happened. The baptised boy was about 16. He just disappeared and no action was taken that I am aware of. We later heard that he got married to a non witness girl. His parents new religion that they started failed and now they are seen around occasionally and that is about it. All this happened about 15 years ago.