The prayer report quoted says:
مَنْ نَامَ عَنْ صَلَاةٍ أَوْ نَسِيَهَا فَلْيُصَلِّهَا إِذَا ذَكَرَهَا
Meaning: whoever sleeps through a prayer or forgets it should pray it when they remember it.
The report gives an explicit sleep-or-forgetting case. It calls for the prayer, not an unrelated alternative.
The same source discussion applies the rational-equivalent reasoning to a fast vowed for a fixed day, vowed prayer and vowed I'tikaf1: their Qada is due without needing a separate new text for each. Keep this reasoning distinct from appointing a substitute that reason alone does not establish.
1. Vowed worship: worship made binding through a vow; I'tikaf is devotional retreat. The example concerns the already-binding duty and its equivalent.
- A Missed Prayer and Other Outstanding Duties