Steven doesn't quite acknowledge the incredulity yet - not until he's had the opportunity to deliver his TOTALLY TRUE and NOT AT ALL EMBELLISHED answer.

"Just a little thing called the sand gem. My team was called in to clean things up, and Lion gave me an assist."

In the sense that for the initial mission Steven sat in the shade while the Gems went to get the crystal themselves, and proceeded to almost cry when Lion approached him out of terror, but whatever. That's not important.