Someone entrusted something to him in the Haram and left it behind; what should he do?

No File Exists
Check below answers in case you are looking for other related questions:
Ruling on requesting a guarantee from a riba-based bank?
It is not permissible for the trustee of a charity to borrow money for himself from the charity’s funds

No File Exists
Related Answers:
Rulings on destruction of property
Ruling on letter of credit issued by the bank
Letters of credit
Ruling on requesting a guarantee from a riba-based bank?
It is not permissible for the trustee of a charity to borrow money for himself from the charity’s funds

Recommended answers for you:
Is it permissible for husband and wife to remove their clothes when sleeping? What effect does that have on tahaarah (purity, cleanliness)?
The reason why the right hand is preferred over the left
Minimum distance of travel at which it is permissible not to fast and to shorten prayers
Ruling on making du’aa’ in languages other than Arabic in the prayer
Suffering From Waswas (Insinuating Whispers) of the Shaytan About the Essence of Allah