The LLM has access to the full text and every translation of it ever produced, both in its corpus and on the searchable web.

The fact that a ring appears at the end proves that the model has context beyond what was in the prompt. The model clearly knows the story that the prompt was extracted from.

This is a rationalization. The simpler explanation is that the model failed to properly depict the passage. As the AI booster crowd would say, cope.