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.
Brick Sloped 30° 1 x 4 x 2/3Light Bluish GrayPart 7835Element 6573768×2
Plates Round Curved and Dishes
3 pieces
Plate Special 1 x 2 Rounded with 2 Open StudsDark TanPart 35480Element 6231386×2
Plate Round 1 x 1 with Solid StudRedPart 6141Element 6141211 spare in the box×1
Tiles Special
3 pieces
Tile Special Round 1 x 1 with Hollow BarLight Bluish GrayPart 20482Element 62588311 spare in the box×2
Tile Special Round 1 x 1 with Hollow BarRedPart 20482Element 6215539 or 61888271 spare in the box×1
Bars, Ladders and Fences
2 pieces
Bar 4L (Lightsaber Blade / Wand)Dark Bluish GrayPart 30374Element 6378143 or 6353308×2
Plates
2 pieces
Plate 2 x 2Light Bluish GrayPart 3022Element 4211397×1
Plate 2 x 4Light Bluish GrayPart 3020Element 4211395×1
Tiles
2 pieces
Tile 1 x 4 with GrooveBlackPart 2431Element 243126×1
Tile 2 x 6BlackPart 69729Element 6318582×1
Tubes and Hoses
2 pieces
Hose, Ribbed 7mm D. 12L / 9.6cmFlat SilverPart 78c12Element 6600686×1
Hose, Ribbed 7mm D. 9L / 7.2cmFlat SilverPart 78c09Element 6600684 or 6081344×1
Bricks Round and Cones
1 piece
Brick Round 1 x 1 diameter Tube with 90 Degree Elbow (2 x 2 x 1) and Axle Holes (Crossholes) at each endFlat SilverPart 25214Element 6335563×1
Bricks Wedged
1 piece
Brick Wedged, Curved Triple 4 x 4 x 2/3, 2 StudsBlackPart 45677Element 4191191×1
Large Buildable Figures
1 piece
Large Figure Limb Cover / Claw / Spike Large with AxleRedPart 15362Element 6549413 or 6291498×1
Plants & Trees
1 piece
Plant, Leaf 2 x 6 x 1 with 2 StudsRedPart 3565Element 6624561×1
Stickers
1 piece
Sticker Sheet for Set 42238-1[No Color/Any Color]Part 10117272Element 6603265×1
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.