You might have better luck trying a live chat on BestBuy website first.
The short version is you didn’t give that store any credit for the sale but you’re asking them to take the full hit for returning it. I want to believe the computer really did think it was out of policy when you tried to return it but obviously I wasn’t there; can’t tell you for certain it’s not just someone being shady. It’s possible an online rep may just give you a prepaid label to send it back for a refund.
If that doesn’t work, I see you used to work for Best Buy. Are you still in the area where you worked? Did you leave on good terms that you might be able to talk to a manager you worked with?