All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His Slave and Messenger.
There is nothing wrong with either expression since nothing takes place except by the Will of Allaah and His slaves have no power or strength except what He provides for them. Allaah The Exalted is the One Who helped you find the lost item and guided you to it. He willed it and determined it. In this sense, it can be said that Allaah has found it for you. This is why the believers in Paradise say what is stated in the verse (which means): {And they will say, "Praise to Allaah, who has guided us to this; and we would never have been guided if Allaah had not guided us."} [Quran 7:43]
Regarding thankfulness, it is proper to combine thankfulness on the tongue by praising Allaah and thankfulness in action by using the blessing in obedience to Allaah. Allaah says (what means): {[We said], "Work, O family of David, in gratitude." And few of My servants are grateful.} [Quran 34:13]
Ibn Katheer commented on this verse saying,
“This indicates that thankfulness to Allaah is expressed by actions as much as by words and intentions. As a poet once said, thankfulness for Allaah for His blessings should be expressed by the hand, tongue and heart. Abu ʻAbd Ar-Rahmaan Al-Hubuli said, "Prayer is thankfulness, fasting is thankfulness, and every good deed you do for Allaah is thankfulness; and the best thankulness is praise." [Ibn Jareer] Moreover, Ibn Jareer and Ibn Abi Haatim reported that Muhammad ibn Kaʻb Al-Qurathi said, "Thankfulness is fearing Allaah and doing righteous works."” [End of quote]
Allaah Knows best.