´It was narrated from Abu 'Abdullah, the freed slave of Shaddad bin Had that:` He heard Abu Hurairah say: "I heard the Messenger of Allah say: 'Whoever hears a man making a lost-and-found announcement in the mosque, let him say: "May Allah not return it to you!" For the mosques were not built for that.'"
Hadith Referenceسنن ابن ماجه / كتاب المساجد والجماعات / 767
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح مسلم
Abu Hurairah reported: I heard the Messenger of Allah ﷺ as saying; if anyone hears a man crying out in the mosque about something he has lost, he should say: May Allah not restore it to you, for the mosque were not built for this.
Shaykh Umar Farooq Saeedi
473. Commentary: It is permissible to make an announcement near the door outside the mosque. «ضالة» refers to a lost animal, while a lost object is called «ضائع». The same ruling applies to it. There is a difference of opinion among the scholars regarding making announcements in mosques about lost children. Some permit it, while others do not. However, in view of human dignity and compassion, there is room for permissibility in this matter, even though most scholars do not allow it.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 473