I've had the very rare missing piece before, but have never received a piece that (according to the parts list) isn't even in the set! Bag 2 in the new Space Shuttle
Sort it out #3: how to identify missing LEGO bricks - YouTube
Missing Pieces – LEGO Certified Stores
Bricks & Pieces - Customer Service - LEGO.com US
Find That Missing Brick With This Lego Parts Database | WIRED
How to get / buy Missing pieces for a set that came incomplete?. Missing pieces for step 5 (179 to 182) specifically in my Millennial Falcon set 75257 : r/lego