With all due respect, RTFM. Mount and umount are two sides of the same operational coin. You mount the drive to use it and unmount it when you're done. fstab is just a file system table used to remember and consistently apply the options used whether you're mounting the drives manually or telling the system to do it at boot.

Deleting a line from fstab is not the same as unmounting, it is just a shortcut to tell the system how you want that drive mounted when you or the system run the mount command. Mount directories (usually the folders in /media/ or /mnt/ ) also do not get automatically deleted just because you "yanked the drive". Again, those directories are just where your system is expecting to mount the drive. When the drive is mounted they will be the root path to its contents, when the drive is unmounted they will be empty but they still exist. If your planning on mounting the drive again leave them there. If you're not planning on mounting them again, delete them.

If you're not planning on regularly mounting a particular drive, it probably shouldn't be listed in fstab and you should just run the mount command with the appropriate options (again fstab is just a table for remembering those options for the mount command).

Many desktop Linux distros are also capable of automatically mounting new removable drives in such a way that the user can access them and doesn't have to worry about touching fstab or the mount directories.