Where is it most likely Matilda lost her necklace in the Necklace?

I assume you mean the story by Maupassant. Struck me vaguely Communistic- at least anti-capitalistic- Cinderella in Reverse gear.- Okay If I follow the story line, she lost the necklace ( en route to the party, at the ball itself- or coming home in a taxicab. There are no intimations of crime- or say- a power failure -cum crime wave- at the party itself. It is not directly stated in the story, but she may have been drunk- and that is why ( is this the Kopechne channel) she did not call up MMe Forestier- assuming they had phones- and this probably was the case- on return from the party- and when she first noticed the expensive (not knowing it was fake) item was missing. She may have been drunk. I don't know how careless one could be to loose something of Hope-Diamond like value even if only a wearing copy. There is not intimation she was mugged, to use a modern term. it is not a crime short story.