When I was a summer relief postman larger packets went out in a van while smaller ones went out with the regular deliveries. Therefore it may not be your regular postman who was unable or unwilling to deliver the parcel.
On one occasion I came outside to demonstrate to the postman who had just delivered a "while you were out" card that I was in fact in. He said he was delivering it on behalf of the postie in the van, who'd been unable to get access earlier in the day. I had actually been in all day but if it was the case then complaining to the postie in front of me wasn't going to do much good…