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 Connector 2 x 3 with Ball Socket [Closed Sides, Squared Ends, Open Lower Axle Holes]RedPart 89652Element 4598440×3
Dark Bluish Gray
4 pieces
Technic Axle Connector Smooth [with x Hole + Orientation]Dark Bluish GrayPart 59443Element 6084613 or 4516546×1
Technic Beam 1 x 2 with Ball Joint Straight, Smooth BallDark Bluish GrayPart 64276Element 6136458 or 6030824×1
Technic Pin 3/4Dark Bluish GrayPart 32002Element 32002199 or 42110501 spare in the box×2
Dark Red
3 pieces
Large Figure Shoulder Cover, Armour, VoroxDark RedPart 64272Element 4582178×1
Technic Axle and Pin Connector 2 x 5 with Two Ball Joint Sockets [Closed Sides] [Open Axle Holes]Dark RedPart 89650Element 4594562 or 4539264×2
Light Bluish Gray
3 pieces
Technic Axle Connector Hub with 3 Axles at 120°Light Bluish GrayPart 57585Element 4502595×2
Technic Beam 1 x 3 ThickLight Bluish GrayPart 32523Element 4211655×1
Blue
1 piece
Technic Pin Long with Friction Ridges Lengthwise, 2 Center SlotsBluePart 6558Element 4514553×1
Bright Green
1 piece
Projectile, Large Figure Weapon, Zamor Sphere / Ball with Marbled Trans-Bright Green PatternBright GreenPart 54821pat0002Element 4296080×1
Trans-Neon Green
1 piece
Large Figure Head Connector Block (Glatorian)Trans-Neon GreenPart 64262Element 4543428×1
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.