DH killed?

[oblr]

FED Rules. DH for pitcher. In the second inning the Pitcher moves to first base and first baseman begins to pitch. In the next inning the umpire says the DH is killed and the "original pitcher/now first baseman" has to bat. We argue FED Rule 3-1-4 says the DH can continue to bat for the "original pitcher/now first baseman" as long as he remains in the game. Who is right? I think he had the rule confused with American Legion which only allows a DH for the pitcher.