Personally I'd be very surprised if this was true, as Pertinax says though it is possible. Also this isn't the only tale of a previously overlooked survivor in a zoo very late in the day. Will Cramp, then a young regular at Hobart Zoo, says that in the mid thirties another animal passed through there on its way to Westbury Zoo.
Thylacines were rare and sought after in those late times, but I don't think they ever impacted much on the public conscious here or back in Tasmania. After all, and despite what you sometimes hear, the last specimen's death doesn't even get a mention in the Hobart Mercury until the following year, and then it's only a passing mention.