When you import a folder of images, the folder will show in the Folders panel, but you may not see the parent folder that it lives in. For example, when I imported my first 2009 shoot folder, Lightroom did not show me that it lives inside my 2009 folder, which lives inside my Pictures folder. That’s exactly where it still was, it was just that Lightroom by default considered this unnecessary information to display. To show this hierarchical folder structure, I simply right-clicked (ctl-click on a Mac) on the shoot folder and selected Add Parent Folder. This revealed the 2009 folder. Then I right-clicked on the 2009 folder, and selected Add Parent Folder again, and this revealed the Pictures folder.
If you like to show the whole structure like I do, just be aware that if you have a parent folder selected, and therefore are showing all images that live in the parent folder and all of its subfolders, you cannot drag and rearrange your images. To do this, you must be in the root folder where the images actually live.