See that long line of connector things that join onto the underside of the drive? Still ain't sure if this is making sense, haha. But yeah, one of those has come off, and you can move it about.
This is one of my old drives by the way. I'm back at my place. He managed to get his drive working by getting the pin back into place, but it's obviously on a temporary solution. He's backing up the stuff on another drive.