That is a good reason to put a second person's name on the lottery request when it is made. The alternate can pick it up.
If no alternate was named, then all you can do is call the Wilderness Permit Office at 760-873-2483, and ask if they would be so kind as to add the alternate for you. (The reason this does not normally occur is to stop hackers from reserving a pile of reservations, and then selling the slots someplace like Craigslist.)
If that doesn't work, you can cancel the permit, and watch for it when the slots show up as available online. (That occurs randomly in the 24 hours after cancellation.) But then you would need to pay another $15 per hiker.
The other method would be to walk-in and request no-show permits (they're free). Your reserved permit becomes a no-show if not picked up by the deadline (10 AM day of entry for overnight trips, noon day before for day hikes.)
