Apparently Garuda have had a system glitch for this day so all flights have disappeared. I got an email advising me of a flight delay and a rebooking via Jakarta but Garuda Sydney (and what a really helpful bunch of people they are, seriously) said DO NOT accept the change. If you do, it'll be at your expense. They did tell their providers about this but obviously Webjet (in my case) sent the email before they go told.
If you've received anything - don't take any action, just sit tight and wait for an update to be sent to you. Or call Garuda in Sydney to get some actual customer service (a rare thing).