Disappering user profile on Macbook Air 13" 2011

Hello aashir.imran,

We appreciate the additional information! Thank you.

If you're seeing a lock icon, it sounds like that could be a prompt for a firmware password as shown in this resource: How to set a firmware password on your Mac

"Your Mac asks for the firmware password only when attempting to start up from a storage device other than the one selected in Startup Disk preferences, or when starting up from macOS Recovery. Enter the firmware password when you see the lock icon and password field:

"

If that's what you're seeing, it may be a good idea to get in contact with the original owner of the device, if possible. This covers how a firmware password might possibly be removed:

"If you forgot your firmware password

If you can't remember your firmware password or passcode, schedule an in-person service appointment with an Apple Store or Apple Authorized Service Provider. Bring your Mac to the appointment, and bring your original receipt or invoice as proof of purchase."

Hopefully this is useful. Have a great day.

Hi aashir.imran,

Thanks for the post in Apple Support Communities. I understand you're not able to sign in to any user accounts on a MacBook Air.

When you say recovery mode is locked, what exactly are you seeing? Knowing this would help work out the steps you might need to take.

When you tried changing the username of the user account on the Mac, what process did you use?

Have you tried resetting the password using the steps here? Depending on the answers to the above, that may be a good starting point: Change or reset the password of a macOS user account

I hope this helps get you started.

Kind regards.