Other mistake: When Leonardo DiCaprio and Jonah Hill are on the sinking yacht with their wives, DiCaprio is holding his wife but you don't see Hill's. Nor do you see her on the Red Cross boat.
Continuity mistake: When Jordan snorts blow from Naomi's breasts, the amount on the right breast suddenly diminishes between shots.
Visible crew/equipment: The first time the movie shows Jordan driving out of the Country Club, high on Lemmon, the front of a camera is visible to the right.
Continuity mistake: When Jordan is flirting with Naomi at the party a woman walks by and tells him that his wife is waiting. Naomi's left arm is raised or lowered depending on the shot.
Continuity mistake: During the Steve Madden scene Jordan says his workers are killers. He holds the mic with his right hand and places his left around a worker's nape. When the angle changes the mic has swapped hands, the hand is gone and Jordan is extending his right arm to grab the nape again.
Continuity mistake: When Jordan introduces Steve Madden to his employees their arms' position differs between the front and back shots.
Continuity mistake: During Naomi and Jordan's water fight over Venice he extends his arms towards her waist and asks for a kiss. Angle cuts and he's away from her, arms lowered. Then she throws the glass of water at him.
Audio problem: After Jordan meets aunt Emma and his pals are dancing, the vocals don't match the singer's mouth.
Continuity mistake: When the marching band shows up in the office a woman twirls a baton and it falls off her hand. A shot later she is twirling it again.
Continuity mistake: When Jordan presents the Oakman logo and brand the paper he holds swaps hands between shots.
Continuity mistake: When Jordan eats with his future partners he tells them to sell him a pen. The hand he holds it with changes between shots.
Continuity mistake: When Jordan goes to his Long Island job his boss talks about two brothers and radars and raises his right arm. From the opposite angle it's lowered and he raises it again.
Continuity mistake: When Jordan's wife finds a classified in the paper he raises a mug and takes it to his lips. A shot later the mug is gone.
Continuity mistake: During Mark and Jordan's meal, the second time they do the chest thumping ritual, in the side angles Leo Di Caprio can't help sneer and tries hard not to burst out laughing. In the front shot he is suddenly very serious. This swaps back and forth between shots. This was due to the fact that the scene was improvised, as Matthew McConaughey once told: https://www.independent.co.uk/arts-entertainment/films/news/matthew-mcconaughey-interview-gold-wolf-of-wall-street-lunch-scene-chest-thumping-tune-film-a7557551.html.
Continuity mistake: During his first day in Wall St. Jordan's boss tells him to pick the "c*ck sucking phone" which Jordan does and puts to his ear. A shot later the phone is gone.
Continuity mistake: When Jordan pitches his first sale at "Investor Center," Dwayne (the guy who interviewed Jordan) is as already facing Jordan, smiling with his head on his hand for support. In the next cut-scene, Dwayne is as being caught off guard to Jordan's pitch and trying to understand what is going on. The scene cuts back to him leaning on his hand smiling. (00:20:00 - 00:20:45)
Continuity mistake: When Jordan is talking with the FBI and their lawyers, there is a box on the table that moves between shots.
Continuity mistake: When Jordan is talking with the FBI agent on his boat, the sun changes between shots.
Continuity mistake: In the yacht scene with the FBI guys, the yacht is alternately docked to its port side with the stern towards open water and with the stern against the dock. When the agents approach the boat, they come from the left side and there is no dock at the stern. When they leave and Jordan throws them bills, they go around the boat's stern via a dock that wasn't there in the first shot.
Other mistake: Story inconsistency, at the start of the film in the Ferrari scene, Jordan says he made 49 million aged 26 as the head of his own brokerage firm. The newspaper article by Forbes states Jordan filed for personal bankruptcy aged 26 and that Jordan is currently 29 and that Stratton Oakmont is 2 years old, making Jordan at least 27 in the scenes when they are still operating from the garage. (00:01:30 - 00:40:00)
Chosen answer: As seen from Donne's reaction when the FBI storm the building shortly after, It should be assumed that Donnie told the FBI himself, and kept the note as evidence. One of the reasons for this could be that Donnie must have felt betrayed or something similar.
Dra9onBorn117