Amazing chess game!
Similar thing happened to me once in a 5th grade school tournament. I was pretty bad at the time, and I had lost my first 3 games or something. In the 4th game, I had my king on the back rank, and my opponent delivered check with his rook and announced checkmate. Without really looking to see if it actually was checkmate, I assumed he was right and in effect resigned the game. Turns out I could have taken his rook with my bishop all the way across the board, but because of how poorly I had been playing for the whole tournament, it didn't occur to me that just because my opponent had announced checkmate didn't mean that it necessarily was.
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