She was never mentioned in canon but assumed dead. Brainwashing, a little bit of hero worship, and a lot of curiosity, tell him to have fun instead! Whatever that fun may be.

Yamamoto blinks. "I'm Takeshi Yamamoto? I play the violin and I'm in a rock band," he said slowly. "I have a mom who works at diner, but I hardly ever see her because she's always pulling doubles."

What more did Squalo want from him?