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 Axle and Pin Connector Perpendicular 3L with Centre Pin HoleLight Bluish GrayPart 32184Element 6276969 or 4211621×2
Technic Pin Connector Hub Perpendicular 3 x 3 Bent with 4 Pins (Pin Ridges Across Part)Light Bluish GrayPart 55615Element 4296059×1
Pearl Titanium
8 pieces
Large Figure Weapon Lightning, with Marbled Blue and Yellow PatternPearl TitaniumPart 98588pat0002Element 6012440×8
Trans-Neon Green
5 pieces
Large Figure Head with HandleTrans-Neon GreenPart 11270Element 6021060×1
Large Figure Limb Cover, Size 3, Armor with Ball Joint SocketTrans-Neon GreenPart 90641Element 6061058 or 4652389×4
Tan
4 pieces
Technic Pin 3/4TanPart 32002Element 6663097 or 60139381 spare in the box×2
Technic Pin Long without Friction RidgesTanPart 32556×2
Dark Tan
2 pieces
Technic Axle 3 with StudDark TanPart 6587Element 6031821 or 6013821×2
White
2 pieces
Large Figure Chest Badge with 'H' Hero Factory Logo on Light Bluish Gray Background PatternWhitePart 98570pat0001Element 6048911 or 6000987×1
Rubber Belt Small [15mm ID] [Round Cross Section]WhitePart 85543Element 6699001 or 4580665×1
Red
1 piece
Plate Round 2 x 2 with Rounded Bottom [Boat Stud]RedPart 2654Element 4617080 or 4278275×1
Trans-Light Blue
1 piece
Large Figure Head / Brain with Glow in the Dark Centre and Marbled Yellow PatternTrans-Light BluePart 11164pat0002Element 6039291×1
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.