It’s a common practice in BFE, and BFE adjacent places to put lost hubcaps, wheels, tires, hats, etc on tree branches or fence posts in the thought that if someone comes looking for it, they can easily spot if and retrieve it. Seldom does it ever get retrieved.

The ancient downhill cyclists totem of goodwill to the tree gods

Somebody placed it there long ago, and now it grows with the tree