Here are some ways you can try out to recover your lost Windows 10 user account:
Log in with another Administrator Account
If you are having another user account on the system (which generally people create) log into that account and try to reset the password for the particular user account that you have lost. Remember, you need to know the password or someone (a family member) having an account on the system and having the access to an Administrator.
Then follow these steps:
Press the Windows key + R
Type there: 'control userpasswords2'
Press the Enter key
Select the particular account and click on Reset password
Enter the new password, confirm it and then click OK
Login with Microsoft account
If you don't have an existing account with Microsoft, create one from the following link:
Then select the situation similar to yours and click Next.
Fill your email address and enter the captcha code that is given.
Then select your preferred method of receiving the code and click Send Code.
Once you get the code, type it and click Next to go to the recover your account page.
If nothing works then the best option would be to undergo a custom Windows installation process. Create a new account and with that, you can recover your personal files from the Windows' old folders and then reinstall your applications and even drivers. It would be time-consuming, but that's the only option which could save your documents. To do this follow these steps:
First, start Booting from your Windows setup media
After selecting your Language, Keyboard Method and Time, click Next
Press Install now
Wait till the Setup starts
Accept the terms and license and click Next
Select a Primary Partition and then click Next
Once the setup is complete, you can then browse through the root of the system drives and recover your personal files directly from the Windows.old folder.