The Border Terrier attacked a man and his puppy and a Destruction Order was issued.
However, a court heard that the dog has been given away and the new owner may not be aware of the risk.
David Leiberman, 71, of Ingram Street, Glasgow, admitted that he was in charge of the dog when it bit Stuart Lygate in September.
He said the Terrier belonged to his wife and he was just visiting her home in Glengowan Road, Bridge of Weir, at the time and it had been left with him.
Sheriff Derek Livingston deferred sentence last month to give the owner a chance to have her pet assessed by behavioural experts, saying that would determine the outcome.
But a Destruction Order was later issued.
Now, in a fresh hearing, Paisley Sheriff Court was told that the owner has given the animal away. The dog is also said to have been allowed to roam loose, chasing locals.
Mr Leiberman's solicitor, Jonathan Manson, said he had no information about who the new owner was and was not in a position to find out as Mr Leiberman's ex-wife was not his client.
Sheriff Livingston said: "This was a completely unprovoked attack on another dog owner and his pet and I am told this is not an isolated incident.
"This dog could act in this way again and it could be a baby next time."
Sheriff Livingston issued a Destruction Order, saying it would be up to the authorities to make inquiries about the animal's whereabouts.