Valid pitching appearance?

[jicecone]

3.08
(a) If no announcement of a substitution is made, the substitute shall be considered as having entered the game when—
(1) If a pitcher, he takes his place on the pitcher’s plate;

This is OBR rules and is pretty common. For a house league I am not so sure I would worry however, I am sure the umpire was just trying to do his job and enforce the rules by the book.