We know how many days passed between when they found Charlie and this episode: 3
Shannon commented to Boone about how he was hanging out with his new "boyfriend" in the woods for the past four days. Since the day he and Locke were out there looking for Charlie and Shannon counts as a day, that makes it three until this episode.
Now, granted, Jack wasn't in his "saving people" frenzy... actually, he wasn't at all... he was commenting on Sun's headache medicine plant >:(
and considering how much he put into trying to get Charlie, I don't buy that he's given up on Claire like that.... Hopefully it was just the sudden jolt of the fuselage getting washed away, and Kate's briefcase thing that distracted him. I suspect we'll find a lot more out about the metal thing in the woods next week.

In the episode's defense, if they were to make an episode all about Jack running through the woods again with search parties for days, with a flashback of, lets say, Kate, looking for Claire, knowing that it would be too harmful to the plot to actually let them find her, would you want it? She's gone. The tracks are gone from the rain. Charlie isn't. The survivors still need a doctor. And they know she's still alive, or at least can think it, so maybe they'll try later... This is the best way they could ease it down... unfortunately... :(