No, it is not a bonsai. It is a aturally stunted tree.
Do not try to bring this home. You will not be able to get it with enough root to survive. Collecting yamadori is a very specialized activity and not something to just do on a whim.
Isn't a bonsai tree just a stunted tree though? what is your definition of a bonsai tree? Wild bonsais definitely exist.
Bonsai is an art. Without the artist there are no art. However, if its possible to sell paintings by monkeys you can call a tree in nature bonsai. The definition is entirely up to you.
