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 Steering Arm 5.5 x 2 with Towball Socket Rounded, ChamferedDark Bluish GrayPart 57515Element 6074651 or 4523398×4
Technic Steering Hub for Portal AxleDark Bluish GrayPart 92909Element 4610378×4
Blue
106 pieces
Technic Axle Pin with Friction Ridges LengthwiseBluePart 43093Element 4309323 or 4206482×9
Technic Beam 3 x 5 L-Shape ThickBluePart 32526Element 4158923×4
Technic Pin Long with Friction Ridges Lengthwise, 2 Center SlotsBluePart 6558Element 45145531 spare in the box×93
Tan
27 pieces
Technic Axle 4 with Centre StopTanPart 99008Element 4666999×1
Technic Axle Connector Ridged [with x Hole x Orientation]TanPart 6538bElement 4207456 or 4140453×1
Technic Axle Pin without Friction Ridges LengthwiseTanPart 3749Element 4666579 or 4186017×3
Technic Engine Crankshaft CenterTanPart 2854Element 6355727 or 6013937×2
Technic Gear 12 Tooth BevelTanPart 6589Element 4565452 or 45145561 spare in the box×5
Technic Gear 20 Tooth BevelTanPart 32198Element 6031962 or 4514557×1
Technic Gear 20 Tooth Double Bevel with Axle Hole Type 1 [+ Opening]TanPart 18575Element 6346517 or 6084724×1
Technic Pin 3/4TanPart 32002Element 6663097 or 60139381 spare in the box×6
Technic Pin Long without Friction RidgesTanPart 32556×7
Yellow
22 pieces
Technic Beam 1 x 3 ThinYellowPart 6632Element 6344174 or 4107823×1
Technic Beam 1 x 5 ThinYellowPart 32017Element 4503425 or 4199343×4
Technic Bush 1/2 Smooth with Axle Hole Semi-ReducedYellowPart 32123bElement 6271167 or 32123241 spare in the box×5
Technic Engine CrankshaftYellowPart 2853Element 6640378 or 4119474×2
Technic Engine Piston RoundYellowPart 2851Element 4112203 or 285124×6
Technic Shock Absorber 6.5L with Hard Spring, Tight Coil in Middle [Complete Assembly]YellowPart 76537Element 7653726 or 6027566×4
Dark Tan
17 pieces
Technic Axle 3 with StudDark TanPart 6587Element 6031821 or 6013821×14
Technic Axle 5 with StopDark TanPart 15462Element 6055631×3
Trans-Clear
8 pieces
Plate Round 1 x 1 with Solid StudTrans-ClearPart 6141Element 6514052 or 62400301 spare in the box×6
Plate Round 2 x 2 with Rounded Bottom [Boat Stud]Trans-ClearPart 2654Element 6581772 or 6163901×2
Trans-Orange
4 pieces
Plate Round 1 x 1 with Solid StudTrans-OrangePart 6141Element 6514059 or 62402271 spare in the box×4
Flat Silver
2 pieces
Hose, Ribbed 7mm D. 11L / 8.8cmFlat SilverPart 78c11Element 4617492×2
Trans-Red
2 pieces
Plate Round 1 x 1 with Solid StudTrans-RedPart 6141Element 6514051 or 62084501 spare in the box×2
White
2 pieces
Light Cover 1 x 1 Round with Internal Bar / Bionicle Barraki EyeWhitePart 58176Element 6194512 or 46231991 spare in the box×2
[No Color/Any Color]
1 piece
Sticker Sheet for Set 42029-1[No Color/Any Color]Part 16179Element 6057511×1
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.