Plot hole: When Sarah Paulsen pulls the necklace out of the water, the necklace clasp is obviously closed. Since the circumference of the necklace is too small to fit over the top of Anne Hathaway's head, why would anyone believe that it fell off her when she was running to the bathroom? The only way that could have happened is if the clasp (which we were earlier told can only be opened by a magnet) had opened. The trained security guards wouldn't have suspected something wasn't right about a closed necklace falling off over of her? They were following her. They saw that at no point did she lower her head on her way to the bathroom for the necklace to fall off over her head to begin with. It also could not have fallen off her when she was vomiting into the toilet in the bathroom since the clasp was closed. (01:18:25)
Plot hole: When the necklace is pulled out of the water (closed) and placed back onto Daphne's neck, they couldn't have used the magnet because the replica didn't have that feature, so the security guards should've noticed the fake right away. To put it back on her neck and to take it off again to go back to Cartier would have required the magnet, which would not work on the replica. (01:18:25 - 01:19:19)
Other mistake: When Helena Bonham Carter removes the necklace from its case, the clasp of the necklace is obviously closed (or at least it should be-otherwise it would slip inside the case itself from the raised mount that it is kept on in the case when the case is being carried) ; she is carrying the top of the necklace (where the clasp is) in her left hand while her right hand carries the bottom of the necklace. Had the clasp been open in the case, her arm and hand motion when she picks it up with her fingers would not have been so smooth. She goes over to Anne Hathaway with the clasp obviously opened (because we see her put the necklace around Hathaway's neck rather than over Hathaway's head) and then she closes it. When she tries to open it a few minutes later the security guard informs her that she cannot open it; that it can only be opened with a special security magnet - which he then proceeds to use to unlock the clasp. In other words, the necklace would have needed to be opened by the security guard to begin with before Helen Bonham Carter could put it around Anne Hathaway's neck. (01:01:05)
Continuity mistake: In the beginning of the movie when Debbie visits Danny's grave she is standing and there is no bench. At the end of the film she goes back to visit Danny's grave and a bench magically appears which Debbie is sitting on and mixing a martini.
Character mistake: Sandra Bullock's German is very good, but not perfect. She says about her husband, "Gestern hat er seine Schuhe in den Gefrierschrank gestellt," ("Yesterday, he put his shoes in the freezer"). Immediately afterwards, she says "seine Schuhe ins Gefrierschrank," ("He put his shoes in the freezer"). The word Gefrierschrank (freezer) in German is masculine and can never be preceded by the accusative case contraction "ins", the contraction for "in das." She just changed the gender of the word Gefrierschrank (freezer) from masculine in the first sentence (correct) to neuter in the second sentence (incorrect). (01:40:05)
Continuity mistake: When Constance begins her 3 card monte game, the mark's $10 bill is sitting with the number facing up. When she starts shuffling the cards, we see the bill again but the number is now facing down.
Continuity mistake: When Daphne talks about the insurance fraud investigation, Rose's hands are on her head in one shot, but in the next shot, her arms are down again.
Character mistake: Sandra Bullock complains that there are no signs that label the areas and directions for visitors correctly. She uses the term "Schilderung", which is based on the word "Schild", which means a sign. However, the word "Schilderung" means description of something, e.g. a suspect, a scene or an experience. "Anweisung" or "Anweisungstafeln" or "Anweisungsschilder" or "Anzeichnungsschilder" would all be valid choices, but not "Schilderung "
Plot hole: The ending sequence is full of holes. 1) How did Nine-Ball get inside without an invite? Sarah Paulson can't work that much magic with the guest list. 2) How did Constance's employers not notice that she was gone - and/or that she was now dolled up with a dress? 3) Same problem for Amhita. 4) Constance, Amhita, and Nine-Ball all have elaborate makeup and hairstyling, the kind that takes hours and several experts to do. Which they don't have.
Continuity mistake: The girl who is in the toilet tearing apart the diamonds is at the same time helping with the food cart with the other jewels.
Suggested correction: The girl tears apart the diamonds, then after the necklace is found, when everyone can go back to normal, that's when she helps with the cart.
Continuity mistake: When Rose is found eating from a Nutella jar, her hands change position on the jar in between shots. In one shot, her left hand is over her right hand, but in the next shot, it's her right hand over her left hand.
Other mistake: Sandra Bullock is walking into a room at The Met Museum where the painting, "Washington Crossing the Delaware, " hangs. When she walks in, there is no picture right next to the left of this giant painting. However, when the security guard notices a crowd gathering at that spot, there now appears the smaller painting of the "Crossing" (which was vandalized by "Banksy"). (00:42:33)
