Falls Update removed my built-in admin acct

Win 10 Home, version 1709 OS Build 16299.19
I had 2 accts. My own admin acct and the built-in admin acct. That has been my habit to have an emergency admin acct.

Today, I've found out the built-in admin acct was gone.
I am not sure if it happened after I installed 16299.15. I did not think of checking because I always leave my computer at sleep mode when not in use with wake up without password
After 16299.19 installed, today I did a Restart and realized the Built-in Admin Acct is missing.
Furthermore, one strange thing has happened. When I signed in, the screen blinked once and came right back to sign in screen. I signed in again, and I got in.
I tried the Switch User option and there was no built-in admin acct.

I am posting this just to find out if someone else has the similar encounter.

Not gone, just disabled.

By default, the built-in Administrator account is disabled. The upgrade to Fall Creators Update has probably reset it to the default. If you open a command prompt and type net user administrator it will tell you if the account is active or not. You should be able to make it active again and carry on as before.

Enable or Disable Elevated Administrator account in Windows 10

I already have the built-in admin re-enabled.

Thank you.

Bree said:

.

By default, the built-in Administrator account is disabled. The upgrade to Fall Creators Update has probably reset it to the default.

That must be the answer why.
Thank you.

davidhk said:

I already have the built-in admin re-enabled...

That's another one to add to my list of 'thing that get reset to their defaults'. Some others I've found are Fast Startup gets turned back on (I had it turned off), Defrag is set to automatically defrag all drives (I had it set to just C:) and the image viewer is set to Photos (I had it set to Windows Photo Viewer). All easily reset, but it's annoying that I have to each time there's an upgrade.