Sorry, you can disagree all you want, but I have purchased Apple items from Best Buy, as I already said my sister has purchased computers from them and I'm currently sitting at a counter with an Apple/Best Buy rep. If you have personally bought computers from Best Buy where is has been on a shelf and the warranty was significantly shorter when you purchased it then that would be one thing but that is not what you said. I have also purchased from an Apple authorized retailer and AASP in my area and did not have this issue.
The only time I have recurrently heard this complaint was from soldiers who purchased Apple devices from the PX several years ago despite the fact that they were supposed to be authorized resellers. It turned out to be a problem with how the military purchasing system meshed with Apple and was eventually brought to their attention.
There was also a time when if you purchased from an AAR you had to go online and register your product and then activate the warranty. Since Apple doesn't do registration anymore this is no longer true.
The OP will need to contact Best Buy to find out what the original purchase date was and then talk to Apple about the warranty.