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.
Large Figure Mask of Earth (Kanohi Pakari)Pearl GoldPart 19077Element 6102760×1
Dark Purple
4 pieces
Large Figure Limb Cover, Size 4, Armor with Ball Joint SocketDark PurplePart 90640Element 6111144×4
Pearl Titanium
4 pieces
Large Figure Weapon Claw, Bent and Notched with ClipPearl TitaniumPart 20252Element 6106738×4
Blue
2 pieces
Technic Axle Pin with Friction Ridges LengthwiseBluePart 43093Element 4309323 or 4206482×1
Technic Pin Long with Friction Ridges Lengthwise, 2 Center SlotsBluePart 6558Element 4514553×1
Dark Tan
2 pieces
Technic Axle 5 with StopDark TanPart 15462Element 6055631×2
Trans-Purple
2 pieces
Large Figure Skeletal, Limb with 2 Ball Joints, and Ball SocketTrans-PurplePart 90617Element 6102836×2
Trans-Neon Green
1 piece
Large Figure Head Connector Block Eye/Brain Stalk (Toa Okoto)Trans-Neon GreenPart 19050Element 6102639×1
Yellow
1 piece
Technic Knob WheelYellowPart 32072Element 6284189 or 4203493×1
Yellowish Green
1 piece
Large Figure Mask Skull SpiderYellowish GreenPart 20251Element 6106711×1
[No Color/Any Color]
1 piece
Sticker Sheet for Set 70789-1[No Color/Any Color]Part 20199Element 6103823×1
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.