I'm afraid, I too am guilty of costing a team not only the game, but the whole entire tournament.
I was plate umpire for an ASA 14U fastpitch semi-final game. The game was pretty ugly, with both teams committing multiple errors. It was the bottom of the 7th, with the visiting team leading by 6 runs. The home team manages to get a one out rally started and has narrowed the margin to one run with a runner on second and third. The runner on third steps off when the pitcher is ready to pitch and is called out. Two out, runner on second. The batter hits a base hit to left center, the runner from second rounds third and is trying for home as the throw is coming in. I realize this is going to be a huge play and make sure I am positioned properly for the play at the plate.
The ball beats the runner by a couple steps, the runner slides, the F2 catches the ball cleanly, mostly blocks off the plate with her body and lays a perfect tag on the runner. An eerie silence falls over the field and I am preparing the ring up the runner to end the game. I hesitate a second to be sure, and as the dust is settling, the runner is laying on the plate, the catcher on top of her and I notice the ball is on the ground. The catcher dropped the ball!!
The catcher quickly scoops up the ball and shows it to me, but too late, I call the runner safe and yell "She dropped the ball!!" You'd think the world had just ended. The visting team went from being estatic to unbridled fury in 2 seconds flat. Coaches are storming out of the dugout, players are crying ...cats and dogs living together...it was pandemonium.
The batter-runner gets to second during the play. Visiting coach is screaming for time (from the foul line). Satisfied that the play is over, I grant the coach time. "HOW CAN YOU CALL THAT BLUE!!!?! YOU MUST GET HELP...GET HELP!" After calmly explaining that I saw the whole thing, the coach slowly retreats to the dugout. Now with two outs, the game is tied and a runner is on second. The next batter hits a screaming double, easily scoring the runner and the game is over.
The visiting coach runs up to me screaming "YOU COST US THIS GAME BLUE, THIS IS ON YOU! SHE DIDN'T DROP THE BALL. THIS WAS OUR TOURNAMENT!! @$#%@)(*%@@"
My partner and I exit stage left and leave the team to finish coming unglued. So there you have it, I have personally cost a team the tournament. Never mind those seven runs they gave up in the bottom of the 7th....
I apologize for this being so long, but this is the closest, most dramatic play I've had to make a call on in my umpiring career. Fortunately, the tournament director and UIC had my back the entire time.
Then there was the baseball game that I balked in the winning run after the pitcher made a fake to 1B from the rubber...