"That child disappears."
Translation:그 아이는 사라져요.
It probably doesnt matter in this case because '그' is responsible for making it specific.
It's similar, but '사라져요' implies 'I can't see the child.' And '없어져요' means 'the child's own existence is gone.'
What difference does it make to the sentence to use 가 instead of 는? Does it change the meaning of the overall sentence?
the child is not acting... it happes to the child.
you would use 가 if the child is actively doing the "disappearing".
but since the tv already disappeared....