Alright, so after getting the SSD yesterday and tinkering around with it for a bit, I've found out a few things:

1. He was lying: it's only detected in the BIOS.

2. He might have done something to it: the warranty void sticker was punctured and the screw underneath was removed.

Welp. I'm going to try and install Windows on it, although I highly, highly doubt it'll work  

Wish me luck guys!