Narrated Abu Hurairah: That the Messenger of Allah (ﷺ) said: "When you see someone announcing about something lost then say:

لَا رَدَّهَا اللَّهُ عَلَيْكَ

laa raddahAllahu 'alaik

May Allah not return it to you. This is because the mosques were not built for this purpose.

Reference: Sahih (Albani). Tirmidhi: 1321