kmp, buy the airline ticket!
You can watch for ones turned in (
here's the link), especially in the week before your hike, but it appears the Day Hike crowd is better at doing that.
If you don't snag one online, go in to pick up the permits, and ask to add. At 8 AM, all permits may still be reserved, but as groups come in and shed a slot or two, those will become available. So start asking about 8:30 when you pick up your reserved set of permits. If none are available, they declare the no-shows at 11 AM, so a bunch will come available then.