What zonepro said.
There have even been natural left handed people who bowl with their right hand that are classified as right handed bowlers. Hell, I even had a guy in college with me who was a natural left hander, bowled with his right hand, and threw a backup ball. Still, he was classified as a right hander.
If the tournament was a sanctioned tournament, next time they have it and he's there, call out the organizer of the tournament and let them know that he's misclassified that bowler and would be against the rules.
BL.