COMBO!
Before Sandshrew can defend itself, or catch a break, Pidgeotto swoops in, knocking it out of the sky with Quick Attack! Sandshrew plummets to the ground like a missile, and when the smoke clears, it's unable to battle.
"No way! You beat me! I guess you deserve this Boulder Badge. Pity. Another trainer taking a badge from a kid like me cause he can't beat the true Gym Leader himself." The trainer said as he chucked the badge at you. The Boulder Badge fell to your feat.
Your Options
Decline the badge until you face Brock on Mt. Moon
Take the badge and forget about Brock