It’s not some hunk of inanimate property, but an animal we are talking about. The animal’s welfare in such a situation does—and should—come into play.
Then animals are no longer private property, they are community property, and thus every pet owner is now immune to any lawsuits involving dog bites.. Legally, it is property. It is private property. Animal or not, this does not change.
And from what I can tell, with the scant information provided, is that the only dumb action by the owner is taking the dog on such a hike in the first place. Everything else seems very much like the actions of a concerned pet owner, including the desire to get his pet back.
Now, if there's any evidence of direct intentional abuse, that's another matter. But until such evidence is provided, I gotta say: The guy's gotta pay for his dog's rescue. He also should get his dog back.