How sad - I really, really hate people who abandon pets of any kind. @errantlight thank you for trying to help the poor little fellow.
I usually fall on the “it’s wild unless it’s provable otherwise” side of the spectrum, but since you likely saw the person who left it, and it was so obviously distressed, I agree with captive.
However, if it had been a species that might have invasive potential in the area, I’d probably vote for it being marked wild - just to document that one was present, because you never know.