You sure can't just whistle one up from Diego Garcia, or much of anywhere else. Even if they had them cocked and ready to roll, it would take, I would guess, at least 15 minutes for them to get airborne, then hours to get to the target. How many hours would depend on just where the BUFF was based. This one must have been the designated aircover for that patrol, or at least that relatively small area.
BTW, it's always nice to see the old girl get in her licks. The newest one came off the Boeing line in about 1964 IIRC. They, unlike active duty and many reserve forces KC-135s, are still using the original engines.