Funnily enough Gildarts being nowhere to be seen even during times such as these is in fact no wonder. From the beginning of the manga the man had a reputation of disappearing for years. So, since he refused the guild master's position, it's only consistent that he's again and still missing. The guild being disbanded for a year is a detail that might even escape his notice, as a single year is nothing for him. It's kind of like a joke, but at least it's well founded.