Here's what I have to say about your situation:
First off, it's good that you were able to get your points back, as most companies are not friendly with rewards points refunds unless you can prove that you did not make the transaction. (Which I think is stupid, because they would have the IP address logs to prove it themselves, which is probably how you got your points back)
Second, if I were you, I would DEFINITELY NOT try to use the PSN codes. GameStop has probably already reported them as stolen or obtained by fraudulent means to Sony. Sony probably has them marked as such, and will most likely BAN ANY ACCOUNT that tries to redeem them. (Not to mention that it would be ethically immoral to try to redeem them anyway, because that would be Theft and fraud by deception)
Third, even though GameStop might have not yet reported these PSN codes as obtained by fraud, I would go ahead and call Sony to report them as such if I were you. Explain how you are a member of GameStop's rewards program, had your account hacked by someone, and that the culprit used your rewards points to obtain PSN codes. Then give the codes to the representative over the phone so they can investigate the matter themselves as well.