**URGENT** - Passport shipment query

Hello everyone,
I’m currently in the US and had a question regarding my passport shipment. I got PPR on 04/09 and sent my passport to CPCO on 04/15 which reached on 04/16. I’ve sent all the necessary documents (customs invoices, return label, photos etc.) but I was under the impression that CPCO will send my passport in a new envelope. Should I have sent a return envelope?
I know the request letter mentions a pre-paid return envelope but I thought that the return label would suffice, which I confirmed with the FedEX associate.
Please advise on the next steps I should take. Also, I read somewhere that if a return envelope is not sent, IRCC sends your passport via regular mail. Is that correct?

P.S. My application was approved on 04/26.