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 45° 2 x 1 with 2/3 Inverted Cutout and no studBluePart 28192Element 6228601×2
Panel 1 x 2 x 1 [Rounded Corners]BluePart 4865bElement 6146218×1
Plate 1 x 1 x 2/3 with Open StudBluePart 86996Element 6432005×4
Plate 1 x 3BluePart 3623Element 362323×2
Tan
4 pieces
Technic Axle Pin without Friction Ridges LengthwiseTanPart 3749Element 4666579 or 4186017×4
Bright Pink
3 pieces
Brick 1 x 2Bright PinkPart 3004Element 4517993 or 4245296×1
Plate Special 1 x 2 Rounded with 2 Open StudsBright PinkPart 35480Element 6588795×2
Opal Trans-Light Blue
2 pieces
Plate Special 8-Sided Crystal/Gem 1 x 1 x 2/3Opal Trans-Light BluePart 65092Element 6514350 or 64469141 spare in the box×2
Yellow
2 pieces
Brick Special 1 x 2 Rounded with Center BarsYellowPart 77808Element 6529612×2
Dark Pink
1 piece
Plate Round 2 x 2 with Axle Hole Type 1 (+ Opening)Dark PinkPart 4032aElement 6326495×1
[No Color/Any Color]
1 piece
Sticker Sheet for Set 77255-1[No Color/Any Color]Part 10115855Element 6585752×1
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.