"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.