It is illegal yes. Bill males tend to stay rather small as per the female can get much larger than a dinner plate. My two males are around 11-12" and quite ancient from an old keeper whom couldnt keep them anymore. They however got put into a release program through TXPW few months back. So I no longer have them.
It is highly illegal to even try to handle one of these tortoises in the wild much less to sell one on craigslist. When I checked the listing it had been removed. In my experience people who know nothing about tortoises will call a sulcata tortoise a texas tort. My guess is that it is most likely a sulcata in an unfortunate situation.