I've just checked the Italo site for out train, it's different to Tren Italia and our Florence train is still listed along with the rest of their services and tickets are still on sale.
Just had look on there for our train, and there are loads to Florence but our specific one at 12.25 is not listed but a 12.10 and 12.35 are but with different train numbers to the one we have. Weird.