Revealing mistake: At the start, when Data is being pulled towards the chained orange drum, due to the angle of the close-up, we see that the soles of Data's Nikes are not actually touching the ground (since there is a rolling mechanism under his feet). Despite the fact that Data is quite inventive, we see in the next shot there's nothing attached to Data's Nikes. (00:03:55)
Continuity mistake: At the start, when Data shoots the suction dart at the orange drum, the drum's scratches, dirt and dents are different in the following shot, as it is being pulled towards Data. (00:03:55)
Continuity mistake: When Data's blue suction dart is stuck to the orange drum and the string is retracting, the thin orange string we saw being released from Data's belt has turned into a thicker brown cord, which pulls him toward the drum. (00:03:55)
Continuity mistake: At the start, when Data's suction dart attaches itself to the orange drum, there are tall metal pieces of junk behind the grey drum which disappear, as the orange drum is being pulled forward toward Data. (00:03:55)
Continuity mistake: When Data starts being pulled towards the bin, the first shot shows him a half foot away from the bin. The second shot shows him several meters away from the bin. Then the third shot that shows Data falling into the bin shows him only an inch away from the bin at the start of the shot. (00:04:05)
Continuity mistake: In the beginning, when the Fratellis are eluding the Police, Chunk witnesses the chase. In the first shot the slice of pizza is on the window. Next shot Chunk holds it in the air, and in the third shot the pizza is back in its place where it was in the first shot, with a saucy smear on the window. (00:04:10)
Continuity mistake: When Chunk runs to the window, to watch the police chase, in the interior shots he stands in front of divided window panes, but in the exterior shot facing him he stands in front of a single pane of glass. (00:04:10)
Continuity mistake: Just after the police chase passes Chunk at the window, the lead police car swerves and hits the road block, knocking it over in the wideshot. Next close-up that swerved car stops right beside the road block, not touching it. (00:04:20)
Continuity mistake: After Chunk does the 'Truffle Shuffle' and Mikey releases the bowling ball, we see the horizontal piece of wood that is painted red and attached to the porch rail, from which the silver bucket is lowered. It's seen in many shots. What's funny is that in the first shot of the Walsh's house, after the Fratellis drive past at the bottom of the hill, that piece of wood is white, because it hasn't been painted red yet by the crew. (00:05:10)
Continuity mistake: At the start, in the second exterior shot of the Walsh's house, after the Fratellis drive past at the bottom of the hill, we see Mikey sitting outside his window beside the small, all black telescope. In the next interior shot the telescope is a different style, it is now grey/black and quite larger. (00:05:10)
Continuity mistake: When Mikey pulls the cord to release the bowling ball, the rocking chair is parallel to the railing, facing the porch, but in the opening shot of the house it was closer to the stairs and facing the yard. (00:05:10 - 00:07:35)
Continuity mistake: Up in the bedroom, when Mikey jumps on Brand who's bench pressing, he grabs hold of the bar and his hand is on the outside, with Brand's on the inside, but close-up their hands have switched. (00:05:50)
Visible crew/equipment: Near the start, when Mikey unlocks the door, just as Mouth steps inside the house the actor's L-shape tape mark is visible on the porch. (00:06:20)
Continuity mistake: When Mouth walks into the Walsh's house, there is a jacket hanging on one of the four hooks in the hallway, but when Mouth opens the door and sees Chunk at the gate the jacket's gone. We know it didn't just fall down, because we can see the floor below the hooks in later shots. (00:06:25)
Continuity mistake: When Mouth first shows up at the Walsh's, in the wideshot as Brand is stretching the chest expander, Brand's left leg is crossed over his right, but in the close-up it's right over left. (00:06:30)
Continuity mistake: There is a rather tall plant beside the Walsh's front door, in the corner, that keeps moving from the corner to the front of the draperies, then back again, throughout the early scenes. (00:06:50)
Continuity mistake: When Brand runs down the stairs to take the paperwork from Mr. Perkins, the large hanging plant that should be over Mikey is gone, but it was there when Chunk arrived and is back later. (00:07:25 - 00:20:25)
Continuity mistake: When Mouth stands by the door cracking up at Chunk's 'Truffle Shuffle' and in more following shots, there is nothing on the wall behind him between the hutch and doorway. After Data breaks through the screen door there is a large painting hanging there. (00:07:30)
Continuity mistake: When Chunk waits to be let in at the gate, Mikey pulls the cord to release the bowling ball and there is a long blue handle (broom?) leaning against the window, but it isn't there in previous and following shots. (00:07:30)
Continuity mistake: When Chunk waits for the gate to open after doing the 'truffle shuffle', a red balloon starts to blow up, but next shot it's a pink balloon that pops. (00:07:40)
Answer: According to Mikey and Mr. Walsh, one of his crewmen must have taken the map and fled when One Eyed Willie was murdering his crew. This is substantiated in the novelization.