Probably the most infamous case happened on July 1, 1991. New York Yankees @ Chicago White Sox. Andy Hawkins pitched an unofficial no-hitter in a 4-0 loss for the Yankees (he pitched for the visiting team in a game which the home team won and only pitched 8 innings. MLB defines a no-hitter with a pitcher pitching at least 9 innings).
Hawkins dominated the White Sox into the eighth inning, where he retired the first two batters. After that, Sammy Sosa reached on a throwing error by Yankees third baseman Mike Blowers. Hawkins then walked the next two batters. That brought up Robin Ventura, who lofted a fly ball to left field. The blustery winds buffeted the ball, and rookie Jim Leyritz, normally a third baseman, booted it, allowing all three baserunners to score. The next batter, Ivan Calderón, hit a fly ball to right field, which was lost in the sun and dropped by Jesse Barfield. The final count for the inning: four runs, no hits, three errors. The Yankees, who had not scored all game, were unable to score in the 9th inning, giving Hawkins the loss.
Baltimore Orioles Dave McNalley walked the bases loaded and walked in the winning run in the bottom half of an away game.
On April 23, 1964 in Houston, Colt .45s' pitcher Ken Johnson threw a no-hitter loss against the Cincinnati Reds. With the score tied 0-0 in the top of the ninth inning, Houston got the first out of the inning. Pete Rose came to bat, and bunted. Johnson fielded the ball and threw it wildly to first-base, allowing Rose to reach second-base on the error. The next batter, Chico Ruiz hit the ball off Johnson's shin to the third baseman, who then threw to first for the second out of the inning. Rose advanced to third base on the play. Next up was Vada Pinson, who hit a ground-ball to second base, but second baseman Nellie Fox bobbled the ball, and his throw to first was too late. Pete Rose scored from third base on Fox's error. Frank Robinson flied out for the third out of the inning. One run, no hits, two errors, one left on base. The Colt .45s went down in the bottom of the ninth to end the game.
July 29, 1968 - George Culver of Cincinnati no-hit Philadelphia winning 6-1.
August 25, 1967 - Dean Chance of Minnesota no-hit Cleveland winning 2-1.
May 17, 1963 - Don Nottebart of Houston no-hit Philadelphia winning 4-1.
April 30, 1967 - Steve Barber and Stu Miller of Baltimore combined on a no-hitter against Detroit losing 2-1.
July 28, 1976 - John Odom and Francisco Barrios of Chicago combined on a no-hitter against Oakland winning 2-1.