deleted user account/ info

i updated my operating system the other night to 10.9.3, when i came up in the morning i had to set up my mac like i just got it with a new user, and I'm assuming it just gave me a new operating system user, and set the mac back its factory state and i can't seem to find the old one. iv gone thru looking at most of the options, can't seem to find the "deleted user" in users or any other place where the old user with all the files on it were. wondering what to to, if the files i lost are replaceable thanks. its my brothers laptop and he doesn't use timeline or anything to back up that i know of. macbook pro

G'day and welcome to the forums.

What does System Preferences > User & Group > Admin Account have to say?

.

it shows one admin account that i had to create to start to mac book up in the register phase, also a guest account.

If you went into Disk Utility and formatted the drive prior to installing, then it's gone - you erased the drive.

how would i know if i done that? would the 10.9.3 update have asked me if i wanted to do that during the set up?

applehelp1555 said:

how would i know if i done that? would the 10.9.3 update have asked me if i wanted to do that during the set up?

Click to expand...

Dumb, I'm assuming the only way the computer could have gotten this way is it had to be done that way manually. I used my brothers computer to play games the other night and there was a window that said I have an update, I put in an hour and then when i was done i never looked back to see what happened. i told him about using the laptop and he was upset. When i woke in the morning it was just sitting upstairs in the first page of setting up the computer (asking for english, united states, ec..) safe to assume this was his doing and not some part of an update the computer did from me?

A simple update would not do that. Even an upgrade from one version of OS X to another would not do that without manually going into Disk Utility and formatting the drive prior to installing OS X.