SSD not being read through SATA but works via USB? Replace the SATA cable.
20 - 30 minuten
Unfortunately there was no interesting story behind this problem. I was just watching a gaming stream on Twitch while chatting it up with some friends when every app and even finder decided to freeze. Couldn't CMD+Q out of anything so after waiting a couple minutes I decided to hold the power and try to reboot.
At that point, SSD wasn't being read anymore. To make sure it wasn't dead I took it out and hooked it up via an external enclosure that goes from SATA to USB. It was instantly read but OSX had gone corrupt. I reformatted the SSD and reinstalled OSX onto it and it booted up/worked fine while it was connected via USB. Putting the SSD back into the SATA port hoping for it to work and I was greeted with a long sluggish recovery screen wait and couldn't even control the mouse..
After taking it to the Apple store they told me they had to order the SATA cable replacement and would call me once to come back in once it's in store. I'm glad I just bought it through iFixit because I'd still be waiting otherwise.. (It's been almost 2 weeks since then)
Super simple, just follow the instructions with the helpful photos. There's honestly nothing more I can say about it.
Just make sure to ground yourself so you don't static shock your MBP into it's next lifetime.