written agreement

my ex partner who is a foreigner and i had a written agreement that he will give the 30thousand pesos he owes me in exchange of his documents like his passport. i did not force him. he willingly gave the documents to me and signed the agreement paper. we had an agreed date and time for the exchange. for some reason, he did not appear and did not give me the 30k so i decided to keep the documents. just today, i received a demand letter from the public attorneys office advising me to return all the docuiments to my ex partner. i find it really unfair because i know he doesnt have any plan to give me the 30k he owes. what is the best thing to do here and what case can they file if i refused to give the documents back? also, him being a foreigner, is he eligible to get help from our public attorney's office? hoping for a reply. thank you.

Also, I filed a case against my partner of RA9262 related to slight physical injury and I want to use the agreement and his passport as my evidences. That is also one of the reasons why I don't want to give it back to him.

does the letter from the PAO refer to the agreement? I would argue that it is a valid deposit for security of the loan.

Yes, it states the agreement but it doesn't say that he is going to pay for the 30k. It's also trying to say that the agreement is not valid anymore because i pursue the case, hence, i should return the documents.

it also states that if i won't give it back, my ex partner will file a lawsuit. what possible case is that and what is the punishment?