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 with Friction Ridges Lengthwise and Center SlotsBlackPart 2780Element 4121715 or 278026×2
Technic Axle Pin with Friction Ridges LengthwiseBluePart 43093Element 4309323 or 4206482×1
Technic Pin Long with Friction Ridges Lengthwise, 2 Center SlotsBluePart 6558Element 4514553×2
Projectiles / Launchers
3 pieces
Projectile, Large Figure Weapon Ammo, Mistika Nynrah Ghost BlasterLimePart 61811Element 4525722×2
Launcher, Large Figure Weapon, Mistika Nynrah Ghost Blaster Air PumpTrans-RedPart 61810Element 4535379×1
Technic Beams Special
2 pieces
Technic Beam 1 x 2 with Ball Joint AngledDark Bluish GrayPart 50923Element 4503381 or 4289258×2
Technic Special
2 pieces
Technic Tooth 1 x 3 with Axle Hole [Rounded Underside]Trans-Neon OrangePart 41669Element 6111281 or 4163574×2
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.