And how do you think humans acquire a theory of mind other than learning behaviors and figuring out what works and what doesn’t?

Oddly, I’ve found that pit bulls won’t wrap themselves around a tree. We’ve had several in our house that are/were walked daily, and we volunteer at a dog shelter where my wife and I walk other pit bulls on a regular basis. There are exceptions, but my experience is that the vast majority will not let anything (like a tree) between themselves and their handler if on leash. Just when I think “ah, ha! You’re going to do it…”, they will course correct and go around to avoid trouble. It’s the oddest thing. I have never come up with a plausible theory, but it sure is nice.

(And it is not our dog handling, as our control groups are happy to wrap circles around a tree.)

Hilarious comment. Without fail, my neighbor's dog wraps himself around the tree within 30 minutes of being outside. It's been 2 years now, and he just can't get the hang of it.

No, because the dog could smell and hear the human, just like they could smell the treat.

Frankly, as a parent of three I'm not at all convinced that human infants lack object permanence, much less adult dogs. I've never observed anything in my infants that would indicate they lost track of something's existence, and I've seen plenty of things that suggest the opposite.

See also the section of that article entitled "Contradicting evidence".