Mens Slow Pitch Question

[Franko]

I have a question about slow pitch softball. The ump called a runner out at third, but then forget he did. A pitch was thrown, the batter got a hit and then the runner scored. When the next batter came to bat, the ump realized he made a mistake and he took the run off. He claimed this was a correctable error. My thought was since the pitcher throw a pitch, the last play was no longer correctable.

who is right?