What do you do when one team forgets that it has an unplayed boule?
What should you do?
Team B had an unplayed boule and was given the opportunity to play next, but refused to do so. Team B therefore was at fault and may not play its forgotten boule. It makes no difference that Team B acted because of a mistake rather than a deliberate desire to cheat. Team B’s forgotten boule is dead.
Note that allowing Team B to throw its forgotten boule would allow Team B to gain an advantage from breaking the rules— it would steal the boule advantage from Team A. On the grounds that a team should never be able to gain any advantage by breaking the rules, Team B may NOT play their forgotten boule.
Note that the situation would be different if Team A had simply gone ahead, without asking Team B if they had any unplayed boules. That would be an ordinary case of a boule thrown out of turn.