Was the game you are referring to blacked out on the MLB Network channel, or one of the MLB Extra Innings channels? During specific days and times, certain national MLB rights-holders have exclusive television rights for distributing MLB games. No games are available on the MLB Extra Innings package during these exclusive national broadcast windows.
Since the game you mentioned was a Saturday game, it’s possible the game fell under the Regular Season U.S. National Live Blackout Schedule rule. Certain Saturday regular season MLB games broadcast live by the Fox network will be blacked out to those end users who attempt to access a live game within the territory of an applicable Fox Saturday broadcast. Learn more at http://mlb.mlb.com/mlb/subscriptions/index.jsp#blackout.