By the logic I'm reading here, if I put a new fountain in my front yard, and someone steals it, it was their right, because when you start putting fountains in places without locking them down, it becomes other people's right to steal them if they can. And that if someone steals my fountain, title to the fountain transfers rightfully to the thief because the nature of fountains is that possession is nine tenths of the law and that transferring fountains (just like cash) is irreversible.
No, when someone accidentally builds a fountain in your front yard, you get to keep it.
You mean to say that if my neighbor puts together his fountain and accidentally does so in my yard, that title to his fountain passes to me? Sorry, it doesn't work that way. By that logic, if I go to an auto parts store, buy a new pair of headlights, and install them on my car in their parking lot (their property), that they suddenly own my headlights and/or my car. Obviously that's ridiculous.
When toner sales men ship you a crate of toner cartridges you didn't ask for, and then sends you a bill for those toner cartridges, you don't have to send them back, and you don't have to pay for them either. Welcome to the real world.