Earlier quoted context omitted.
How does that even happen? I have pre-check, and it's always been an entirely separate line. They'd have to do a fair amount of work to redirect you over to the 'regular' line.
It used to happen only at smaller airports that didn't have the capacity to handle extra lines. But lately, I've had it happen at bit airports (like ATL), so I'm not really sure. The answer to your (implicit?) question is that it doesn't work. The staff take the card from you at the start of the process, and once your bag is in the machine, they have no idea if it's yours. So far, every time this has happened, I"ve b…
If I sound confused, it's because I am :). I don't get a pre-check card, it just shows up as a notation on my boarding pass. I scan it just like normal, then shove my phone into my backpack and toss it on the belt. No removing my shoes, belt, etc.
They also won't touch my bag, and I have to be the one to push it onto the feed belt of the scanner. They have to have a pretty good idea that it belongs to me.
Coincidentally, I just travelled through ATL a few weeks ago. It's never as smooth as my home airport (PDX) because it's a much busier airport, but I don't recall anything out of the ordinary happening.