There are some things in Sitecore that you just take for granted will work. Loading items is a good example of this. I'll admit that user error can get in your way, but usually if you can see an item in the content tree, you can write code that will load it without issues. So I'll admit I was pretty confused when I came across a scenario recently where this did not appear to work correctly. In case anyone else hits this challenge, here's what happened:
There's been a bit of discussion (I might even go as far as to say ranting 😉 ) on the subject of not using "fast query" in your website code recently. I'm a supporter of this idea – but I came across an issue recently that points out why it's not always easy to be confident that you're not making use of it indirectly...
So, for the benefit of Google: