The tire shop I use is a full serivce tire shop, vehicles, tractors, log skidders, heavy equipment you name it if it has a rubber tire they will deal in it.
They have a few large clear plastic jars (like those oversized cheese puff jars) full of stuff found in tires. It amazes me every time I go in there what new piece they have found in a tire. I guess the strangest I have seen was a .243 Winchester round, yes live ammo, that went through a tire and for some reason did not go off. Primer was still intact, case was mangled and the bullet was pushed into the case quite a bit.