Bob managed to don a New York Yankee uniform in their spring instructional camp in 1958. But his real claim to fame was his unbelievable record with the Alexandria Aces of the Evangeline League in 1957. His won-loss record was 20-0! His low ERA of 2.21 no doubt helped. His accomplishment was so unusual that he was featured in a Believe It Or Not presentation in one newspaper I ran across.
The attached photo is from the Wellslville (NY) Daily Reporter of August 27, 1957, and shows him in his Alexandria uniform. For a better quality version of the same photo, the viewer might want to check out the display on baseball-birthdays website at:
Baseball Birthdays Forum - View topic - Minor Leagues
Robert Riesener Register Statistics & History | Baseball-Reference.com