Right on. I have used my metal detector to find errant practice shots that scoot under the pine needles! It's a valuable tool in camp.
The graphite ones do have aluminum inserts, and even the plastic blunt tips for squirrels have an aluminum shaft inside.
I haven't lost one to squirrels yet, but did have to return the next day once to find one sticking up at the base of the tree just as you say! I believe the thieving beast lost his grip on my arrow as he slept
I did leave a razor broadhead 15 feet high in a tree after being led into hitting it by a turkey. I was shooting across a small ravine and THWACK. I tried to shimmy up to get it, alone, way out in the woods, half mile from camp, 40 miles to a hospital, 700 miles from home, for a five dollar bent and dull toy. It's still there.
Hunting or other rec camps sites are loaded with junk so good discrimination is needed, but the chance of something of interest lost must be high. I'm missing a fine skinning knife, and if it doesn't turn up I've got to get back and search!