Lightroom Classic - mobile device sync

When you removed the folder, you would have received a warning message telling you that photos in that folder would be removed from the Lightroom catalog. When you go ahead and remove, all the images in that folder are automatically removed from the cloud also, so you should also see that they have been removed from the Lightroom app on your phone.

Because they are not automatically deleted from the local hard drive, you should be able to reimport them again....but you will have lost any editing and other metadata which you may have added (unless you save metadata to XMP as standard). You should find them on your C drive, in a folder called "Mobile Downloads.lrdata" in the Pictures/Lightroom folder. When you import them again, they will not automatically sync to the cloud, you would need to manually do that by either adding them to a synced collection or adding them to the All Synced Photographs special collection in the Catalog panel.

Note that if you don't want that iPhone "Drive" to appear in the Folders panel when you sync images from the phone, you can change the storage location on your local hard drive to a "normal" folder....see the Classic Preferences>Lightroom Sync tab.