It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) used to make this supplication about something lost: "O Allah, O Restorer of what is lost, and Guide out of misguidance, You guide out of misguidance: return my lost thing to me by Your power and Your authority, for it is from Your gift and Your favour."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13232