The Worst Error You've ever made reffing a game?

[Freddy]

My very worst was . . .
Boys' frosh game, two-man with a Slinky partner. Five seconds for home inbounding team, down by two, to go length of court to launch a shot to tie or win. Clock not easily visible to me in extremely noisy gym, with fans, players, and coaches all screaming, as ball is dribbled past a picket fence of defenders, each a potential fouler I had to keep an eye on. Dribbler coming inches from touching sideline in front of benches, which I had to keep an eye on. He launches an off-balance three-point attempt with defender's hand up and nearly blocking the ball, which I had to keep my eye on. While my eyes were engaged on everything necessary, my ears were not--I could not hear the horn. Shot went in. Was it in time? I could not tell. Slinky partner, with nothing whatsoever to do this whole time was no help since he had checked out and assumed I had all aspects of this play as my exclusive responsibility. I went with my gut and banged it "Good!" and ran to the locker room.
Scorer, a trustworthy veteran, came in and asked what I thought. I told him. He said, "Wish you woulda asked me. The buzzer went off before the shot was released." He was from the home team, but woulda informed me that the visitors had won if I had checked with him at the table.
Lesson for me: better diligence on last-second shot responsibilities. And, since the book does consider any information the scorer might have as valid input to consider, consult with them before making a final decision if necessary.
There, I feel better.
Still trying to "burn the tape" on that one.