The Wife w'pointers...
Hi, Hubby is the Shroud'd one, I'm the cat one, the cat obviously is traum'd, if the cat is in your den or used place, try to move it to a spare room, give it food, water and litter box, and basically leave it alone, go in give it it's food etc, and go sit, just sit on the floor or whatever, and talk to it, don't approach it. Possibly it is shy, unsocialized to anyone, maybe your friend didn't have many people over and the cat was used to just him, eventually he will come around. My mother got a cat from a barn, who was terrified, and was never really socialized. They are creatures of habit, but give the kitty the space and respect he needs. He will come around.
We had a cat that showed up our doorstep, she was totally wild and seemed feral, we fed her, gave her some shelter and one day out of the blue I opened the door, she came over, I asked if she'd like to come in, and she did.
Maybe get a cat tree or something tall kitty can get on top of they feel very safe when up high.
The Wife