You don't need a permit to hike as far as Lone Pine Lake. Beyond that, the permit is required and the entry date matters.
I suppose a ranger could see you were backpacking in on the lower trail and ask to see the permit.
But you can likely get a no-show or cancelled permit for your friend in the week before the hike. Some good people do log into Recreation.gov, and cancel their unused permits early enough for people like you to get them. Set up a link to that site for the date you need, and check it daily, and in the week before, as often as possible.
Otherwise, as people are picking up permits, they shed a few due to some people dropping out of their group, and those become available immediately at the Visitor Center where you pick up permits. The Visitor Center opens at 8, there will likely be no-shows available on the morning he needs to hike. (There will likely be some available on the morning before the entry date, but those wouldn't be any good for your friend, since he would need to be there to pick up the permit.)
Check the
Unused Whitney Permits 2012 info. You can see that there are almost always some unused permits available. These numbers are what was left
after everyone like your friend walked up and asked for a permit.
