Maybe the recipient could pop down to his local callers office (before 2pm) and ask to speak with a delivery manager - ask for his assistance and explain the situation- help get to the bottom of the situation
I’ve completed investigations and given postmen warnings around leaving packages (not SD) in porches- customers have complained they’ve not received them - only to have the eagle eyed postman spot the empty packages in the recycle bin a few days later- I’d rather leave a P739 card the next time they have a package( in no way saying that’s the case here)