Question: If a player starts to expose tiles on their rack, and then says, oops I can’t do that because they don’t actually have Mah Jongg, can they put their tiles back?

Answer:  Since they did not verbalize, “Mah Jongg”, the player must first complete the exposure after calling the tile and can then return their other tiles to their rack. Had Mah Jongg been declared and the hand incomplete it would have been a Mah Jongg in error.

Source: NMJL Bulletin 2022 (added after a letter was written to the NMJL by a player)