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 Knob WheelYellowPart 32072Element 6284189 or 4203493×1
Energy Effects
3 pieces
Large Figure Weapon Accessory, Flame / Lightning Bolt with Axle Hole with Marbled Trans-Light Blue PatternWhitePart 11302pat0003Element 6266807 or 6029783×3
Technic Beams
3 pieces
Technic Beam 1 x 2 Thick with Pin Hole and Axle HoleBlackPart 60483Element 6265091 or 6006140×1
Technic Beam 1 x 2 ThinBlackPart 41677Element 6338428 or 4167726×2
Technic Bushes
3 pieces
Technic BushLight Bluish GrayPart 3713Element 6275844 or 62718171 spare in the box×3
Technic Connectors
3 pieces
Technic Axle Connector Smooth [with x Hole + Orientation]BlackPart 59443Element 6084612 or 4512363×1
Technic Axle and Pin Connector Perpendicular 3L with Centre Pin HoleBlackPart 32184Element 6276951 or 4121667×1
Technic Axle and Pin Connector Angled #1WhitePart 32013Element 6332573 or 4118981×1
Technic Special
2 pieces
Technic Ball Joint with Through Axle HoleBlackPart 53585Element 4286267×2
Stickers
1 piece
Sticker Sheet for Set 70788-1[No Color/Any Color]Part 20043Element 6103072×1
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.