When you search for files on your computer using Windows Search via File Explorer or Cortana, the files you expect to find may not appear in the search results. This happens even though the files exist on the computer.
Another situation is that some phantom files appear in search results, whereas you may have deleted the files long back. In some cases, the searches may be very slow whether or not the folder location is included in the index.
This post tells you how to fix Windows Search issues in Windows 10 and earlier.