"I didn't know what to do but jump up and down for joy," Stefani said, according to The Associated Press.
After the ball went in, Stefani walked the length of the 213-yard par 3 and kissed the sweet spot where it landed, according to the AP report.
He did not donate the ball to the USGA Museum, but instead donated a signed glove and scorecard. Merion is hosting the major tournament for the fifth time. Stefani was under par for the day, but finished the tournament at 19 over par.
Joey Nowak is a reporter for MLB.com. Follow him on Twitter at @joeynowak. This story was not subject to the approval of Major League Baseball or its clubs.