The return policy should work fine even if they don’t have any in stock. Unfortunately we can’t exchange an item for another if we don’t have it. In instances where it is an item that is hard to get and you don’t wish to make a straight return, have you considered using the manufacturer’s warranty to get a replacement instead? The burden and obligation of that warranty would be on them. Best Buy, as the retailer, merely facilitates returns and or exchanges within your return period. As long as you are allowed a return in accordance with that policy, Best Buy has fulfilled their obligations.
I am a Best Buy Employee, but the views that I post are my own and not that of Best Buy.
***Know that I am not able to issue official responses and that my posts are only here to help before an official response is offered by a Best Buy Social Media Specialist***