Every time I've had a missing piece so far it's actually turned out that it had got stuck in the corner of a bag when I was pouring it out and I hadn't noticed!
Yeah, I have this all the time. Yesterday i checked every corner of every bag I opened, and nope... Luckily it was easily substituted by two 1x1's.
You're lucky it was a common shape and easy piece to substitute, so at least you have that going for you. Of my over 1000 sets I've only encountered it like 5 times that I recall. Honestly, it's just amazing to me LEGO is so precise at getting every tiny piece right ALMOST all the time in every box. So if I'm missing something common now and then I can't even hold it against them, haha.
I only have around 40 sets, and it's the first time. It is in a very large set though, so I reckon mistakes are more easily made there. Bit stupid it's in my first really big set (largerst after this are my modulars). But yeah, Lego has a terrific track record. Compare this to what Jang encountered with Mega Bloks (whole bag missing from his Enterprise)...
I'll build the thing and then mail Lego (maybe there is another piece missing) for a replacement anyway though. It's a piece that is easily reached and replaced and after spending 350 euro I want the damn thing the way it should be
150,000+ pieces and this has happened to me twice. A 1x2 jumper on Fire Brigade, a clear window insert on the Simpsons house, and Plo Koon's goddamn head from the Anti Vehicle Cannon. I recently found a clear window insert behind my shelf so I suspect that was a user error.
The Plo Koon thing pisses me off to no end though. TLG wouldn't replace it for me.
That sucks. I can imagine Lego has to deal with scalpers trying to get doubles of rare pieces by claiming they missed one in the box, so they are reluctant to replace them. Sucks to be the victim of that, as I can even imagine you got that set for the figure alone (it's a cool build, but it's the figure that shines)