hard drive not recognizable

a blank drive is always "unrecognizable", by definition.

Use Disk Utility to ERASE the ENTIRE drive, by its immutable manufacturer-name. If the immutable manufacture-name is not showing, choose "show all devices" to see it, and do not proceed otherwise.

Internet Recovery can provide Utilities like Disk Utility and allow you to make progress.

Try running the Apple Diagnostics to see if any hardware issues are detected. Unfortunately the diagnostics don't detect many drive failures.

If when you boot into Recovery Mode or Internet Recovery Mode and the physical drive does not appear on the left pane of Disk Utility, then the drive has most likely failed, but there is also a chance the hard drive SATA Cable may be bad which is very common on the MBPro 13" (mid 2012) non-Retina model. Within Disk Utility you may need to click "View" and select "Show All Devices" so that the physical drive appears on the left pane of Disk Utility. When erasing a drive on an Intel Mac it is always best to select the physical drive to erase. For a 2012 Mac, erase the physical drive as GUID partition and MacOS Extended (Journaled).

If you have a Retina model does it use a third party SSD? If so, then you must boot into a macOS 10.13+ installer since older versions of macOS are unable to work with third party NVMe SSDs.

If you have access to another Mac from 2010 to 2019, then you can use it to create a bootable macOS 10.13 to 10.15 USB installer if you have trouble with booting into Internet Recovery Mode:

How to create a bootable installer for macOS - Apple Support

A 2010 to 2017 Mac can download & create a bootable macOS 10.13 USB installer, while a 2012 -2019 Mac can create a 10.15 installer.

Hi jpnewkirk,

Are you sure the hard drive is completely dead? Try these steps:

1. Power on your Intel-based MacBook Pro while holding down Command-R. Release the keys when the Apple logo and a progress bar appear, or when a spinning globe appears. In the latter case, select a Wi-Fi network to connect to, in order to download macOS Recovery.
2. In macOS Recovery, select Disk Utility and click Continue.
3. In Disk Utility, select View -> Show All Devices.
4. Does the internal drive appear at the top of the sidebar?