لَمْ نَرَ النَّجْمَ الْمَنْتَظَرَ. لَمْ يَظْهَرْ لَنَا أَثَرُهُ.
We did not see the expected star. No trace of it appeared to us.
If the second clause reinforces the same non-observation, complete connection can justify leaving out wāw. The later expression makes the same assertion more explicit or forceful rather than supplying an independent event.
This is not necessarily an answer to the question “Why did it not appear?” That would require a cause. Faṣl may arise from both reinforcement and explanatory resumption, but the reason for faṣl is different.