Amazon refunded my $690 GPU after it was delivered. What should I do?

About a week and a half ago, I ordered a high-end graphics card for about $690 that was sold and shipped by Amazon.

Because of the value, the package was supposed to require either:

• a one-time passcode that I would provide to the driver, or
• my signature before it could be delivered.

I also scheduled it to be delivered to my neighborhood leasing office on a specific day because I knew I'd be at work.

Instead, Amazon delivered it early while I was at work. No one asked for the one-time code or a signature, even though those were supposed to be required. The tracking initially showed the package as delayed, even though it had already been delivered.

I contacted Amazon as soon as I realized what happened because the delivery instructions weren't followed, especially after an Amazon support rep had previously assured me it would be delivered on the scheduled day. The representative apologized for the delivery issue, and since I already had the GPU in my possession, I figured everything was resolved.

Fast forward to today, and I got an email saying the delivery had been cancelled, and Amazon automatically issued me a full refund.

So now I have both:

• The GPU, and the refund.

I never asked for a refund, and I didn't report the package as missing. It seems like Amazon's system canceled the order after it had already been delivered.

My question is: What should I do in this situation?

Should I contact Amazon and explain exactly what happened, or just leave it alone since the refund was issued automatically? Has anyone experienced something similar? If I don't contact them, is there any chance Amazon could later recharge me or take action against my account?

I'm mainly looking for advice from people who've dealt with something like this before.