In case of lost items, one of the most beneficial Duas to recite is from Surah Al-Baqarah, Ayah 156:

Inna Lillahi wa inna ilayhi raji‘un

إِنَّا لِلَّهِ وَإِنَّآ إِلَيۡهِ رَٰجِعُونَ

Although this Dua is most often heard when someone passes away, it can also be recited in any situation of loss. This Dua is a reminder that everything ultimately belongs to Allah, and He has the power to return it to you if it is good for you.

Recite it with sincerity and trust in Allah while searching for your lost item.