I don't want to get into another argument, but the files download in the background and do not install right away. They even go into a hidden file waiting to be fully complete and then ask if you want to update. It is just a thought and has happened to several with no other visible signs.
The folders to look at are:
C:\Windows\SoftwareDistribution\Download\8f36b36c5f97d84a69eedf4ec27435ec folder, and check if there is a file with the name formatted as BITXXXX.tmp XXX as random characters or numbers. The file may be several GBs in size, which provides evidence that download of Windows 10 is still in progress and not yet completed.
So yes, you can get 4 GB of Windows 10 download, not be notified, and not see any obvious changes in your computer as Windows 10 was not installed yet. Again, just something to check, nothing more.