My question involves criminal law for the state of: CA
I bought a gift card from someone for $500. That person made copy of the card and used it after he sold it to me.
Police and many detectives and my friend set up a trap and caught him on the act with all evidences including receipts he spend from my card after he sold to me, videos showed he sold the card to me then used the copy one to pay at self check out. Photocopy of the card that he was about to sell.
After police got all info from him, they let him go. I received a police report with all evidences against him but it said: 'Case closed'. 'Forward to DA for review'.
My questions:
1/Why the police did not arrest him since they got adequate evidences?.
2/How long does it take for DA to review and prosecute?.
3/Is it possible that DA decides not to prosecute him?
4/What can I do to follow up with the case?
5/How can I get my $ back?

Thanks a lot for your advices.