itch.io

Thanks for confirming... I was thinking maybe it's because it can't be utilized yet.  Also possible it's by design to be extremely frustrating.  Another theory, maybe you need the backpack?  I haven't purchased it yet but assume it will increase my inventory capacity.

Possible SPOILER

I found it in the corner of the server room of the Lima antenna.  Wanna say day 5ish, maybe...

The rifle does exist in-world... I found it.  It was too heavy to add to my inventory at the time, so I tried to carry it outside but when I dropped it it immediately broke.  Not sure if this is a bug or by design.