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 Beam 1 x 2 with Ball Joint Straight, Smooth BallDark Bluish GrayPart 64276Element 6136458 or 6030824×2
Technic Beam 1 x 3 with Ball Joint in MiddleDark Bluish GrayPart 98577Element 6001085×1
Technic Pins
3 pieces
Technic Pin with Friction Ridges Lengthwise and Center SlotsBlackPart 2780Element 4121715 or 278026×2
Technic Axle Pin without Friction Ridges LengthwiseTanPart 3749Element 4666579 or 4186017×1
Animal / Creature Body Parts
2 pieces
Animal Body Part, Barb / Claw / Tooth / Talon / Horn, SmallWhitePart 53451Element 6270106 or 4568387×2
Containers
2 pieces
Barrel Half Large with Axle HoleReddish BrownPart 64951Element 4541875×2
Technic Special
2 pieces
Technic Ball Joint with Through Axle HoleBlackPart 53585Element 4286267×2
Projectiles / Launchers
1 piece
Projectile, Large Figure Weapon, Zamor Sphere / Ball with Marbled White PatternTrans-Light BluePart 54821pat0007Element 6075061×1
Transportation - Sea and Air
1 piece
Technic Cylinder 4 x 4 with Pin Holes and Centre Bar, Closed Sides on BarPearl TitaniumPart 41531Element 6074417×1
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.