Yes, you would have to bring in the ad during the promotion and while the store that is pricematched against has the merchandise in stock

We call this negative pricematch, meaning that Bestbuy does not adjust the price unless per request by the customers.

Think about it, many people think that Bestbuy has the best prices and that's why they shop there. If a customer does not know about a lower price elsewhere and pays 10 dollars more at Bestbuy, that is 10 dollars more profit for Bestbuy. Why should Bestbuy adjust the price automatically in the store when the customer is unaware of a lower price then?