If you did not open the product then the customer service associate would not open it to do the return - that would usually make it so Best Buy can not resell it. If you opened the product and resealed it, the associate will open it to verify all parts are inside prior to doing the return.
So hypothetically let’s say someone returns a shrink wrapped empty box and leaves before the box is opened are they allowed to open the box without the owner there or are they required to attempt to return the property to the owner before opening their property
They would most likely do neither and put the item in "customer abandonment" until the customer returned (they will hold items generally for 120 days before recycling them/throwing them away). You leaving the product there without discussing it with the associate nor waiting until the transaction is completed does not put the onus on the employee to track you down/complete your return. I'm sure if they had your rewards information from your recent (assuming you're a rewards member) they could call you to verify what you want to do, but they will more than likely check the package - especially if it feels abnormally light (aka, empty).
I do indeed and I participate in the forums during my off time, so my views are my own and not representative of the company. However, I have a lot of knowledge around Best Buy and their policies and poke around here to try and alleviate some of the work load for the forum moderators.