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.
Cone 1 x 1 [Top Groove]Bright Light OrangePart 59900Element 6482736×1
Brick Round 1 x 1 diameter Tube with 90 Degree Elbow (2 x 2 x 1) and Axle Holes (Crossholes) at each endDark Bluish GrayPart 25214Element 6501503×2
Animal / Creature Body Parts
2 pieces
Animal Body Part / Plant, Tail / Vine Curled with BarDark AzurePart 1997Element 6573667×1
Creature Body Part, Horn (Unicorn)YellowPart 89522Element 6573657 or 62234201 spare in the box×1
Technic Beams Special
2 pieces
Technic Beam 3 x 5 Thick [90° Offset Centre Beam Holes]BlackPart 14720Element 6390379×2
Mechanical
1 piece
Pullback Motor 6 x 3 x 5Dark Bluish GrayPart 12799Element 6143751 or 6024100×1
Stickers
1 piece
Sticker Sheet for Set 42220-1[No Color/Any Color]Part 10115266Element 6580512×1
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.