When I was my college's team manager, we had a guy disciplined and he missed at least one game, if not more.
The next game he was eligible for was the first game of a weekend tournament. Me, doing what I normally did, simply carried forward the roster from the previous game, not remembering this player was not in the book. So, when he enters the current as a participant, he's in neither my score book nor the official score book, resulting in an admin T.
The worst part was that a high school classmate played for the opposing team in that game. For a number of years after that, he never let me live down this moment and the fact his team won. Thankfully, the T didn't affect the outcome.