@Mike: Thanks for that link - those aqua-pouches and emergency water bags are pretty cool! I might get one or two...
In the "what if you lose your pack" scenario department, I always hike with a GG Hipster with the pouch part in front ($15 and just under 1.5oz on my scale). Mostly, it's for convenience of having some things right there (even easier to get into than pack hip belt pockets). Size is just right. It only comes off when I am in the tent. In a particularly isolated area, I might sleep with it on. Contents on any given morning when hitting the trail are usually as follows:
-Trail snack food to eat on the go (not all of it, just enough until the next time I rest and refill from my pack. Usually at least 3 or so packets of Justin's almond butter in addition to bars, small baggies of fritos, nuts and raisins, VIA packets, etc.). These are stuffed on top of everything else and may make it a little too full at first, but only until I eat something. Overflow can go in a pocket.
-Map and compass there for easy access to check navigation
-Very small little Rite in the Rain notebook and wee mechanical pencil for notes.
-Hand sanitizer, eye drops, lip balm with sunscreen, ibuprofen
-Tiny folding knife
-I also have one of those AMS mini survival kits in a wee waterproof zip pouch in the hip pouch, containing a magnifier, signal mirror, fishing kit, backup compass (tiny), whistle, needle and thread, scalpel blade, duct tape, foil, nylon cord, wire, safety pins. While I'm comfortable on my sofa, I could easily work out how best to use these items, but knowing that if I need to use them, I will likely NOT be comfortable, and may be fighting the urge to freak out, I left the written instructions in the kit for when my brain shuts down...
I also will temporarily stuff other stuff in there or hook them on the belt part, like toileting items when off to dig a cat hole (hooked on belt in pouch, not in with food), or tent stakes as I'm pitching to make sure they're not lost if I am worried they'll fall out of my pocket. I also keep two empty dog-doody cleanup bags in there that are the perfect size for trash - some of my own (wrappers for bars, etc.), but also for trash I pick up on the trail (it's a compulsion, I can't leave something once I see it. Bottle caps, bits of plastic, clothing labels, reflectors that have fallen off bikes...). Once trash bag is a bit more full, I carry it in my pocket instead of the hip pack.
I have not included more robust fire-starting stuff (though there's stuff in the little survival kit), because it's been so dry (strict burn ban/stove ban) that if I tried to start a fire, I'd probably be more likely to start and then be caught in a giant wildfire!
I usually don't keep my head light in there, but it's tiny, so now that I think about it, I'll add it next time. I also don't have something for a shelter. I have an emergency blanket/bag I carry, but it doesn't fit in the little hip pack. Haven't figured that out... Oh, and something to carry water. I'm going to take a look at those emergency water bags.
Anyhow, I mostly use the little hip pack not because I'm paranoid about losing my pack, but because I like to have certain things very easily accessible. But I decided that if I was going to carry emergency survival stuff, it was kinda dumb to put it deep in the pack if I was wearing a hip pack, too.
Now I'm just wondering whether I can get a set of bagpipes into the back pocket of my Circuit. Hmmm....