Parcel in the toilet?
My Dad told me a story of my mother's 21st birthday. He bought a bunch of red roses for her to be delivered to the house. He went to take her out that night and my Grandad told him to go away as my Mum wasn't very happy he had forgotten her birthday present. Despite protests, he left. Next morning they went into the outside room 100 and there they were!! No card through the door or anything. Maybe the florist sisn't think they'd have a bog upstairs as well 
Mark
Groan. It's one reason I hate courier deliveries. Some even come equiped with feaher dusters to rattle the letter box. Even though I have a notice on the door to RING THE BELL. Why is that so difficult.
The only people that seem to do a decent job, round these parts, is dare I say it, Royal Mail. The postie saw me getting into the car the other day, cut short his round, came across and said he had a parcel for me. And if I do miss them, they take it to the nearest post office (one round here seems to be open nearly all hours and on a Sunday!!!) or back to the sorting office, which is a sight more convenient than a trip of 30 miles or so away.
The other delivery method I use quite often is the local drop off and collect. Anything to avoid a courier delivery.
Back in my television repairman days c1970, nothing was ever more annoying when you are in a bit of a hurry (apart from dog poop on the drive or a carpet soaked in cat pee behind the TV) than an unanswered door when they were supposed to be home, a house name that was not displayed, no number, no door bell... and a sticky knocker. 
Being a multi drop delivery driver must be the number one rubbish job and I should know - I tried it for a week. 
The only problems with delivery is the complete inconsistency. Take RM for instance. If I'm not in parcels are either left hidden somewhere (behind my bin or in it usually) or a "while you were out" note is left with instruction to pick up at the local sorting office.
And I'm still surprised at what they do sometimes. A couple of days ago I found a large parcel behind my bin. What I found odd was that it was a recorded delivery signed for parcel. I don't remember signing for it.
Well it was amazing just how many times I'd be sat in the van writing out that "while you were out" card and they would suddenly appear saying "were you just knocking on my door, we were home y'know"
"Sheesh, then try answering it" I'd mutter under my breath. 
@billnotben One comment I read was from a guy who had a new bin delivered, and he did even not notice!
I suspect that responsibilty is with the driver.
Given their probable turnover of staff somebody would have a full time job on their hands. As a company car driver of many years I cannot recollect even being asked by them for my drivers licence... but maybe my memory is fading.