Re: Sure . . .
But you have to remember that Afghanistan is a big place, and the border to Pakistan is long, largely unguarded in the early weeks of the war. Anything could have happened.
Captured? Possibly, but I doubt it. You could keep their identity secret, sure, but not their security. Omar and bin Laden would doubtless require huge security measures, which would be very noticeable to the media. They might not know who was caught, but they would know it was someone very, very important. And we would know that "someone very, very important" was being held.
Dan