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.
Technic Pin Connector Hub with 2 Perpendicular AxlesBlackPart 10197Element 6099801 or 6098801×1
Technic Pin Connector Hub with 2 Pins with Friction Ridges Lengthwise [Big Squared Pin Holes]BlackPart 87082Element 4560174×1
Technic Pin Connector Round [Slotted]Flat SilverPart 62462Element 6245499 or 6054858×1
Bricks Curved
2 pieces
Brick Curved 4 x 1 Double, No StudsDark BrownPart 93273Element 6135005×2
Plates
2 pieces
Plate 1 x 1BlackPart 3024Element 3024261 spare in the box×2
Technic Beams Special
2 pieces
Technic Beam 3 x 0.5 Liftarm with Boss and Pin Semi-ReducedBlackPart 33299bElement 4563044×1
Technic Beam 5 x 5 x 2 Perpendicular Fork 3 FingersDark Bluish GrayPart 19086Element 6102645×1
Technic Panels
2 pieces
Technic Panel Fairing #21 5L Small Smooth, Side BDark Bluish GrayPart 11946Element 6330085 or 6197965×1
Technic Panel Fairing #22 5L Small Smooth, Side ADark Bluish GrayPart 11947Element 6352665 or 6197945×1
Technic Special
2 pieces
Technic Ball Joint with Through Axle HoleBlackPart 53585Element 4286267×2
Bars, Ladders and Fences
1 piece
Light Cover 1 x 1 Round with Internal Bar / Bionicle Barraki EyeLight Bluish GrayPart 58176Element 6212288×1
Technic Bushes
1 piece
Technic Bush 1/2 Smooth with Axle Hole Semi-ReducedLight Bluish GrayPart 32123bElement 6271165 or 42115731 spare in the box×1
Tiles Special
1 piece
Tile Special Round 1 x 1 with Hollow BarBlackPart 20482Element 6186675 or 61679331 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.