2♣ was announced as "Intermediate", ie natural with opening values. They were playing Precision.
2NT was intended as unusual, showing the lowest unbid suits, but was not alerted. N/S asked, and East told them it was 15-18, balanced, with a club stop.
The TD enquired: they could not remember ever running into a Precision 2♣ opening before, and they really had no agreement whatever.
South said he led the ♦8 because he expected all the points to be on his left, and would have led a safer lead if he had known the position. After the lead ran round to the jack and queen, declarer ruffed a club and played a spade to the ten when North did not split, only losing two hearts.

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2♣
2NT P 4♠ P
P P
Result:
4♠/E +1
NS -450
Lead: ♦8