Missing Macintosh HD after wipe

[Indymom]

My daughter bought a Macbook Air from a close friend of hers. The friend followed directions to move her info and wipe the laptop. When my daughter got it home to set up, she couldn't get the OS to install. She tried several times, gave up and contacted Apple support through chat. They tried the same exact method she had already tried, then moved on to other fixes. She followed their directions, trusting that they knew what they were doing in order to get the laptop up & running. They had her deleting things. Now she has no startup. The only thing showing in Disk utility is the SSD. Macintosh HD is gone. Nothing shows up in Time Machine, just mentioning since we've come across it being used in fixes. So, we've tried everything we can find to figure this out, but to no avail. Im clueless when it comes to Macs, as I'm not very familiar with Apple products, the lingo, etc. Any help, direction and/or advice would be greatly appreciated. Here's the info about the laptop:

2015 Macbook Air
Model A1466
13 inch screen
Last OS was Sierra

If there's any other info that's needed, please let me know. Thanks in advance !!

 

[glenthompson]

At this point you may need to use internet recovery mode. Turn the machine on and hold command-option-r until it boots. It will ask to login onto your WiFi. Once that is done you can to create the disk partition and install the OS. It will need to download about 4gb for the install so don’t be in a hurry.
Lots of instructions online, just search for Apple internet recovery.

 

[NoBoMac]

Here's Apple's page for internet recovery.

How to reinstall macOS - Apple Support

You can use macOS Recovery, your computer's built-in recovery system, to reinstall the Mac operating system. Reinstalling macOS doesn't remove your personal data.

support.apple.com

 

[Fishrrman]

INTERNET RECOVERY

Press power on button.

IMMEDIATELY HOLD DOWN
Command-OPTION-R
... and KEEP HOLDING IT DOWN till the next step.

You'll need your wifi password.

If internet recovery is working, you'll see a "spinning globe".
It will take some time to load, be patient.

You should see the internet utilities.
The one you want is the OS installer.

Open the OS installer and begin "clicking through".
The Macbook may reboot one or more times, and you should see the "progress bar" one or more times.

When done, you should see the initial setup screen ("choose your language").
Begin setup.
You'll probably need to create an account.

You haven't told us what kind of backup your daughter has (time machine?).
Some of her personal data (including an old account) MIGHT already be on the MacBook (we don't know that).

But the first order of business is to get an OS installed and an administrative account set up and running so you can "get to the finder".