Maybe the satchel was found when they went in for the arrest? idk..
Maybe Morgan -was- bi. But something's really off about it, in my mind.
Morgan was attacked lying down, or sitting, wearing only a tshirt.. sure this could suggest a gay sex fling. But it could also be that the killer waited for the lights to go out, tried the door, found it open (for the flatmate, maybe) and removed Morgan's pants after the attack, or even in his sleep (creepy thought).
Just trying to give Morgan the benefit of a doubt here, as we only have his killer's word for the 'Morgan wanted sex' thing. And like I said, it just seems all a bit weird to me.
I guess we'll see. If Morgan was bi, no doubt somebody will yak about it sooner or later..