According to the note, what remains possible regarding Zayd in “Zayd came—rather, Amr”?

Particles of Meaning: Waw, Fa, Thumma, Bal and Lakin

• Zayd’s arrival is conclusively established
• Zayd may or may not have arrived; his non-arrival is not conclusively asserted
• Zayd’s non-arrival is conclusively established
• Bal independently establishes both Zayd’s and Amr’s arrival