Sherlock Holmes and the Missing Pearl

I have been replaying Sherlock Holmes and The Mystery of the Persian carpet. I got to the ladies sitting room and the balancing of the 9 pearls puzzle. I balanced all the pearls against each other to find the two lightest ones only to find that there was only one lighter than the rest which made it impossible. So I came out of the game - went back in - and low and behold there were only 8 pearls. Now - how can you drop a pearl on the floor in a computer game Weird Huh!

Anyone else had strange things like this in a game?