If you're using WP Media Folder and Advanced Custom Field's image field, the uploaded Media just wont show up in the generatet folder if you're switching file-upload dialogs. Example: When I set the post-image, I create a folder, upload 3 images and choose one of them. When I then switch to ACF's image field to include the other ones, the folder exists, but the images aren't there. Only after saving/updating the post they'll show up.
Solution 1: Media Folder should update content when the media-dialog opens or
Solution 2: Add a Reload button
I think this feature is needed / bug should be fixed..