The visitor tried to save it from drowning, after which reintroduction to the herd failed. Want to make it clear this wasn't a tourist just trying to openly grab a baby bison.
Still don't think this was appropriate (for the visitor to do) as the rule of these parks is to not interfere.
What do you mean by failed?
Often times, a baby animal who had contact with humans is rejected by the herd because it has traces of human scent on it. It smells like a predator. Birds display behavior like this too, which is why you should leave baby birds undisturbed if you find a nest.