When you import from a memory card device, that same memory card device is also available to be selected in the Destination panel, so almost certainly you've inadvertently selected that device as the target drive.....so basically Lightroom reads from the card and copies the same files back to the same card. That's why that folder appears in the Folders Panel, with the folder and files listed as "missing". Unless you use the "Make Second Copy" option (which is what that option is there for), then I'm afraid you're correct that you've lost those pictures.
If you haven't re-used the card after re-formatting, it might still be possible to recover some/all of the images using dedicated card recovery software.
So you're thinking I may have accidently clicked the memory card in the Destination panel?
That would be my guess. It's the only option that I think fits the scenario.