Firstly: There is no authentic evidence to support the recitation of Sūrat aḍ-Ḍuḥā forty times or seven times as described in the mentioned narrations or reports.
Similarly, there is no authentic narration indicates the recitation of Sūrat aḍ-Ḍuḥā in the case of losing or misplacing something.
Secondly: The absence of specific evidence for such matters does not imply that there is no merit in reciting a particular surah in a specific situation. Allāh informs some hidden aspects of supplications to some His creation that may not be known to others, as mentioned in the authentic Ḥadīth: “or [I pray to You with one of Your Names] of which You informed one of Your creations.”
Many scholars and Imāms have experienced reciting specific surahs in specific situations, and Allāh guided them through it.
Reciting Sūrat aḍ-Ḍuḥā a certain number of times in the case of losing something has been practiced by many scholars, and by the grace of Allāh, it has helped some of them in their time of need. I have personally tried it on occasions, and it has coincided with success in some instances while falling short in others.
Therefore, it is permissible to recite Sūrat aḍ-Ḍuḥā in the case of losing something. However, it should not be assumed that this is a prescribed practice or that it is explicitly mentioned in the sayings of the Prophet (peace be upon him). Making such assumptions without evidence falls under baseless claims. The matter is open for personal choice. Those who wish may recite it without any objection, but it should not be considered a binding ruling, a specific wisdom, or a guaranteed benefit. All such things are based on clear-cut evidence and not subject to personal reasoning.
Fatwa issued by Dr. Khālid Naṣr