Recent return to Amazon, my wife got me a Legos Creator kit (one with six sets of bags, probably 2500-3000 pieces). I started working on it, and was missing a piece. Now I'm pretty organized with my Legos. I open all of the bags for each step and keep the contents separate. I searched through all of the opened bags, the box, the floor and could not find it. Finally gave up, figuring it wasnt a critical piece and skipping for now wouldn't hurt anything. Started finding more and more missing pieces before realizing, I was missing a piece or two, but an entire bag of pieces.
My wife returned it and Amazon sent a replacement the next day. All my wife has to do for the return is drop it of at Kohls next time shes out running errands. Pretty painless really.