[danielobvt]

Looks to me to be a "keep tank", they may be referred to as drop tanks, but the past reality has always been to KEEP them.
Could they have dropped it to increase the aerodynamic profile of the aircraft if they were doing something that required the full performance of the aircraft? What that could be over Afgan, I do not know, but is that a possibility?

[Cliff Dweller]

If performance is an issue, then we have been under-engineering our platforms. Delivery of ordnance typically doesn't require the extreme edge of the envelope flying. The only thing enhanced by dropping it is reduced parasitic drag, (or in some cases increased drag because of the loss of an aerodynamic store).

In any case, it found its way to earth, perhaps looking for added benefits from a dumb luck hit.