Can a DH be taken out of the game and in his place hit for by the player he was hitting for?

Question
Here is the situation...from the beginning of the game, we were batting 10, and we were DHing for our 1st baseman.  Midgame we decide to take the DH out of the lineup (hitting like crap) and replace him with the 1st baseman he was hitting for.  Two ASA umpires told us that cannot be done, and we protested.  The game was a championship game, and we were up at the time, and ended up losing.  Am I crazy in thinking that it is a simple substitution?  Please let me know what you think.  Thank you very much!

Answer
Hi Michael,

With batting 10 I assume this is slowpitch?  

In slowpitch we do not have a DH (ASA does not use the term DH) or a DP or a FLEX, we have an EP.  With an EP all 11 bat and any 10 can play defense.  

So you must a local league rule that allows you to use a "DH".  I'm surprised you cannot sub in the person that he is batting for (as you can with a dp/flex combo in fp) but stranger local rules are around.

Mark