It’s really important that you review your backup software from time to time. One to check that your backups are actually working but more importantly to make sure you are still backing up everything you need too. Quite often you add new folders and sometimes the backup is not told about the new location.
If on the other hand, it’s a subfolder within a folder you’re already backing up then there is a high probability this will be caught, but please do check.
Review the content from time to time that is being backed up too, as you might find that you are backing up unnecessary data and in some backup systems you are limited to how much you can store.