Rule out the usual hiding places first. If the piece really is gone, check the set piece by piece
and leave with the element ID LEGO asks for, or a link to buy the part.
Projectile, Large Figure Weapon, Zamor Sphere / BallBright GreenPart 54821×1
Launcher, Large Figure Weapon, Zamor Sphere Launcher, Bottom with Axle HoleRedPart 98564Element 6021671 or 4652056×1
Technic Pins
2 pieces
Technic Pin with Friction Ridges Lengthwise and Center SlotsBlackPart 2780Element 4121715 or 2780261 spare in the box×2
Bars, Ladders and Fences
1 piece
Bar 1L with Clip [Cut Edges and One Side Hole] [Gap in Clip]Light Bluish GrayPart 48729bElement 6278156 or 45425901 spare in the box×1
Tick each piece as you find it, or mark it missing.
When a piece really is missing
Ask LEGO
LEGO takes requests for pieces missing from a new set through its customer service site. The form asks for
the set number and each piece's element ID, the number printed beside the piece in the parts list at the back
of the instructions. This checker lists both.
Mark a piece missing and your list links it to an eBay search for that part, which also covers pieces from
older or second-hand sets.
Keep a record
Copy or download your missing list (the CSV opens in any spreadsheet), or print the whole checklist and tick
pieces off on paper. Your marks stay in this browser, so you can check a big set over several sittings.