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.
Large Figure Armor, Crystal with Marbled Trans-Light Blue PatternPearl GoldPart 24166pat0002Element 6135071×4
Large Figure Mask of Ice (Unity) with Marbled Trans-Light Blue PatternPearl GoldPart 24150pat0002Element 6135000×1
Large Figure Mask with Back with Marbled Trans-Light Blue PatternPearl GoldPart 24162pat0001Element 6135049×1
Blue
4 pieces
Technic Pin Long with Friction Ridges Lengthwise, 2 Center SlotsBluePart 6558Element 4514553×4
Pearl Titanium
4 pieces
Large Figure Skeletal, Connector with 2 Ball JointsPearl TitaniumPart 24189Element 6139106×1
Large Figure Weapon Lightsaber Hilt with Axle Hole and Two Bar HoldersPearl TitaniumPart 24122Element 6135325×1
Technic Axle Connector 2 x 3 QuadruplePearl TitaniumPart 11272Element 6251539 or 6022718×2
Dark Blue
2 pieces
Large Figure Limb Cover, Armor, ShoulderDark BluePart 90650Element 6135226×2
Dark Tan
2 pieces
Technic Axle 3 with StudDark TanPart 6587Element 6031821 or 6013821×2
[No Color/Any Color]
1 piece
Sticker Sheet for Set 71311-1[No Color/Any Color]Part 24842Element 6135256×1
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.