Yes, we are our own editors 99% of the time. This was actually written by my editor and he must have missed that.
Here's the thing, doing a copy edit on your own stuff is very hard. You read it in your mind that it's correct, even when you have things like this pop up.
That and the fact that we're writing thousands of words a week, running the magazine, putting out fires, and doing all kinds of other stuff things get missed.
Now you know why I don't hang out in chat anymore