I am sure it did not take long to inspect the runway (27L). I suspect the inspection found some bits
How long do you think it took to log / photograph their positions, and possibly get AAIB clearance to move them? And then thoroughly clear the runway.
No doubt all true, though it doesn't invalidate the proposition (widely reported in the press, though of course that's no guarantee of accuracy) that adequate fire cover was temporarily unavailable for normal operations on 27L.
Out of interest, what happened in the immediate aftermath of BAW38? Were sufficient RFFS resources held in reserve to support an immediate switch to single-runway operations on 27R? Obviously there was no requirement on that occasion to inspect the other runway.