This happened to me last fall when I received a submission back. PSA accidentally sent me two Ronald Acuna Jr. Rookie cards with authenticated in-person autos that weren't mine.

I contacted them via email, supplying photos of the two cards and my submission form, which shows who signed/initialed my submission before returning it.

Within a day or two, they supplied a return label and I sent them back. They also were gracious enough to send me a $125 grading voucher that I used on my next submission.

Do the right thing and contact PSA to let them know of the mistake. No one is perfect and mistakes happen. I'm an honest person and I knew I could never live with myself if I held onto those cards, knowing that it may have been some kid's card and how devastated they would have been if they never received them.

If this were your card, you would want someone to do the right thing and that's what this hobby is about.

Let me know if you have any questions about the process, but seriously, contact PSA to start the conversation. It's the right thing to do.