A man pitched a nine inning game and didn't let up a hit or walk and made no errors yet he lost 1-0. How?

He could have hit 4 batters in the same inning which enabled one to score.

Note: HBP does not count as a walk.

I just thought of another possibility.

The batter could have been HBP and stole second and third and the batter can just hit a grounder or fly ball and the runner will score.

There are lots of ways a batter can reach first without getting a hit, walked or an error. The pitcher could throw a pass ball on a third strike, which will show as a srike out with the runner advancing to first base, there could be a catcher's interference in which the batter is awarded first base or the batter could get hit by the pitch. Also, your scenario didn't say if the game was a 9 inning game or went extra innings. Perhaps the guy pitched 9 innings of 0-0 ball, then on the first pitch of the 10th inning he hit the batter. If the coach pulls him and puts in a new pitcher, then the next batter came up and hit a triple, then the startring pitcher would lose the game 1-0 without ever giving up a hit of his own. He would still get charged with the run scored since the HP led to the runner getting on base. Fun question :)

There's other ways of a man reaching base and coming around to score. Hit by pitch, catcher's interference, passed ball on strike three. Once on base, he could advance by stealing, fielder's choice plays (not likely though; would have to be another baserunner teammate), groundouts, sacrifice bunts, a sac fly to score.

It's not easy scoring a run without a hit or a walk, but it can be done.

Ken Johnson lost his 1964 no-hitter, 1-0, when Rose reached on an error (by Johnson himself -- Rose made it to second base), advanced on a groundout, scored on a second error. Yeah, there were errors and Johnson issued a few walks during the game, but the point is that a run can be scored under unusual circumstances.

Someone else may know the answer better, but is a beanball an error? If not, four beanballs in an inning would do the trick. Or one beanball, and the greatest base stealer in history.

Maybe 4 batters got hit by a pitch and that's how the run was scored.

extra innings, a reliever came in and pitched 9 innings didnt let up a hit, walk or made any errors

Catchers interference. Stole 2nd and 3rd. next batter sac fly. 1-0

He came into the game with no outs after the starting pitcher had allowed a run.

he could have hit a batter, or thrown 4 illegel pitches, then when the battter was on base he could have stole bases, or there also could have been wild pitches to move the runner or there could have been illegel pitches to move the runner

hit by a pitch or balk and a fielder's choice