Should I be talking to the supervisor?
Let's clarify this:
The thing was delivered to you without your awareness.
You are not obliged to return it. It's Apple, the error maker, to retrieve it from you, with proper paperwork at your house.
So if you think you are kind and generous enough to deliver it back to an Apple Store, I would suggest you do it properly and bring all the boxes, wrapping and deliver bill. This will help Apple track their issues and improve in the future.
And to be sure that what you do will benefit all relevant parties, at the cost of your time and effort, you should require proper paperwork for your return. i.e. at least a receipt should be issued to record their acceptance of the return.
The below is an example where I live. Not relevant to Apple, just common paperwork, even if you are kind and generous. It's to protect yourself.
I received a chunk of money transferred to my bank account.
I then later received a phone call, the caller identify himself as the sender of the money and asked me to transfer back the money.
In this case, if I took it for granted and use the money, I would face criminal charge.
But if I was too eager to do good and wire back the money without any verification and proper paperwork, that transfer would be still counted on my own responsibility as well. Some others even were scam when the money was deemed as a debt, with enormous interest rate.
So in my case, I left the money untouched, just informed the bank about the money and waited for their instruction. I requested the whole legal paperwork (exclamation, explanation etc.) from the sender, with the bank verification before allowing the bank to correct the transaction. I did not make the transfer slip as if I wired the money back at my own will.
In this modern world, being good and doing good are simply not enough. You need to do it properly as well.
If you are indifferent and lazy like I am, then I would suggest you just call the police and report about a wrong delivery, with purpose unknown. Make it an official police report and leave the package untouched. That's all the law require a law-biding citizen to do.