I walked in the LP ranger station and got a permit on a Saturday in August a few weeks ago. The ranger told me they have issued walk up permits to all that have asked this year. I'm not sure if there are more cancellations than normal this year, but it sure seems like it. To be on the safe side, you need to be at the permit office at 11:00 am the day before you hike, which is when they start issueing permits that have not been picked up.
Good luck, and have a great trip!