Fantastic news, congratulations and thank you for sharing your experience!
You shouldn't be surprised USCIS didn't take your Philippines passport. US government cannot take away foreign passports (only hold temporarily for issuing visa etc). The Philippines passport is a property of Philippines 🙂
Now, you may be obliged to report your acquisition of US citizenship to Philippines, and they may take your passport. But you should learn, I think there is a more or less straightforward procedure you can undergo to reinstate your Philippines citizenship. If you want, you can be a dual citizen and enjoy benefits of both countries. But you would be subject to laws, duties and restrictions imposed by both countries too.