The Case of the Stunt Man

Case of the Stunt Man

One sunny morning, a kid named Alex Hertingz came into the detective agency and said, “I have a case for you.”
“What is it about?” asked Nicole. “Murder?”
“Well, sorta.” says Alex. “My dad, the stunt man named 'The Great Herting' was killed during a stunt.
“The Great Herting!” exclaimed Nicole. “Why, he is the most famous stunt man in the United States! He also has the biggest rival, Camorma the Great.”
“They saw that he was not on the motorcycle when it landed from his motorcycle stunt.” Alex sniffed a little. A tear fell down his cheek. “I went to his funeral a few days ago."
“How did you have a funeral without a body?” asked Nicole.
“With a costume that fell from the sky.” said Alex, pointing at the sky.
Suddenly, Alex said, “Your father wasn't killed, he was kidnapped by a rival plane while he was up in the air, but they left a clue that was told in your story, and showed in your actions.”

What was the clue? Leave your guess in the comments.

Bobo