They couldn't have had him two weeks ago - when Brandon released him, Prince George had first crack since they were lowest in the standings. The only way Calgary could have gotten him before that would have been to make a trade with Brandon. And maybe the Wheaties were asking too much, and/or didn't want to trade Cowan to an Eastern team. Who knows.
And P.G. didn't trade him because they weren't happy - it's because they have too many OA's there and need to get rid of two. They need defence more than they need forwards, so Cowan was the odd man out.