if a batter is injured during an at bat and leaves the game with 2 strikes. Sub then strikes out on first pitch he sees - I am assuming the sub is charged with the K even though he only saw one pitch?

Good question -- but in OBR there's a definitive answer.

10.17 (b) "When the batter leaves the game with two strikes against him, and the substitute batter completes a strikeout, charge the strikeout and the time at bat to the first batter. If the substitute batter completes the turn at bat in any other manner, including a base on balls, score the action as having been that of the substitute batter."