What is the ruling if a follower joins the Imam in Jumu'ah before Zawāl, catches one rak'ah, and then misses the prostration (sujūd) of that rak'ah, assuming the prayer converts to Dhuhr?

Primary text

If a follower catches one rak'ah of the Jumu'ah prayer led by an Imam who prayed before Zawāl, and it is held that this prayer converts to Dhuhr, yet the follower misses the prostration of that rak'ah, the entire prayer reverts to being a voluntary (nafl) prayer. This is decreed so that the Dhuhr prayer is not considered performed before its proper time.