My "Reply to Thread" button is all goofy. I had to "Go Advanced."
Regarding the fire pit....
While I think it's a possibility a fire pit might suggest some avenues for further investigation, I have several issues:
1. Not everyone, by any means, actually builds a fire when they camp. This would be especially true if one was trying to stay hidden. Personally, I never ever build a fire when camping, car camping, backcountry, any of it. I haven't built a fire since 1983 or so, and I've camped out hundreds of nights, including a homeless stint in a free camp spot.
2. A fire pit in the vicinity of the corpse might not have belonged to the UID.
3. The UID may have used a stove that got stolen.
4. The UID may have eaten sandwiches.
5. The UID might not have been killed /died in the vicinity of the nearest fire pit. Perhaps he crawled to the spot where he died?
6. A fire pit could have been buried by the perp.
7. If the location has certain characteristics, there could have been a flash flood that would wash things away, including fire debris and other evidence.
8. Is there any water at that location? If not, the UID would have had trouble camping; it it's dry there (as I understand it is) the UID would have got very thirsty. If he had a dog, the dog wouldn't have liked going waterless one bit.
What might be productive is to dig through the debris left in nearby fire pits to see if there's anything relevant. Car keys? The rest of a dog collar with tags? Insignia for a motorcycle gang? Some of the fire pits in the backcountry have years and years have stuff accumulated under the top layer of charcoal.
The homeless scenario seems kind of unlikely to me unless we extend the concept to include rock band groupies, Burning Man attendees, and miscellaneous random travelers.... That place seems remote and not to have much to draw a homeless person. It was free, though, and it's hard to find free camp spots (you have to kind of know about them). I can't really figure out what that location would be on the way to or near. However, I am thinking the UID was hiding and knew someone was after him. Drugs, maybe. A sneak. A card game that went bad. A gang. Settling an old score....
I'm not sure I could see a homeless person killing someone for their shoes or much of anything a homeless person might have on him (except maybe money). Homeless folks can get fully outfitted (and gladly) at a shelter or outreach program. There are some generous and thoughtful people out there, and a place like Reno would have had a place to get handouts (e.g. a church), a good meal, a replacement coat, a sturdy pair of boots. Reach-out centers have showers, stuff like razors and shampoo, soup and bread, and sometimes a ride to another location or a warming place if it's cold out. Homeless folks know where the services are: it gets around.
A chance meeting between two homeless folks might be a difficult occasion for a random stabbing, because there'd be no way to know if the potential victim was armed, e.g. with a knife. I'm thinking it would be stupid to pick that kind of a fight.
I'm also not certain that a homeless person vs. homeless person scenario would result in hands and feet cut off and removed from the site. A homeless person walking off with hands and feet? Stashed in a back pack? Wrapped in newspaper? This seems just too weird.
The dog could have belonged to the perp and not the UID? The dog ran off when a marmot was sighted and the perp couldn't get him back and felt he needed to leave quickly? The dog got loose when the perp came back to check on the corpse and not at the time of the stabbing?