Riyad as-Salihin, Book 18, Hadith 1698 (In-Book) ⓘ

Buraidah (May Allah be pleased with him) said: A man announced (the loss of his camel) in the mosque, uttering these words: "Has any one seen my red camel?" Upon this the Messenger of Allah said, "May it not be restored to you! The mosques are built for what they are meant to be (i.e., prayer, remembrance of Allah, acquiring knowledge, etc.)."[Muslim].

وعن بريدة رضي الله عنه أن رجلا نشد في المسجد فقال‏:‏ من دعا إلى الجمل الأحمر، فقال رسول الله صلى الله عليه وسلم ‏:‏ ‏ "‏لا وجدت، إنما بنيت المساجد لم بنيت له‏" ‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏