Ken for something to happen post the landing assumes that the crew knew they had scraped the pod.
I don't think it is a given that they knew they had dragged the pod and given it was pissing down and not many people I know do post flight inspections it is not unreasonable that it wasn't immediately reported.
As for the preflight inspections, I think there has been plenty of discussion that indicates the difficulty in identifying the damage given the location so put it all together and the fact that the damage went unidentified for a few days is not surprising.