https://www.lego.com/en-us/service/replacementparts/missing/enter-set-number

Let Lego know, they'll send you the right pieces.

Yeah, now they can wait weeks while the toy is half built. About as useful as when ikea sold me a bed frame without support beams for the mattress and Said i had to wait six weeks while my bed was disassembled

I ordered a missing piece this past month and it showed up in 3 days.. ymmv sounds like.

Are you sure you didn't use those pieces by mistake earlier in the build?
Go back and check.

Every time I've though Lego has screwed up, it's been me not being very careful. Or my cat...

Facts I used to build Bionicles and messed up so many times

Happened to my son's very expensive BB8 set a couple years ago. & bc covid was at it's height, no Lego store. We're STILL waiting on a replacement piece. Figured we slipped thru the cracks somehow and tossed the whole set. Bummer