When is a sheet not a duvet

When is a sheet not a duvet, when it's a sheet !! That's obvious isn't it ?
My little world was invaded by aliens at roughly one thirty this morning when a contingent of the Welsh light infantry (with some heavier detachments) arrived on my doorstep.
They came like waifs and strays, creeping out of the dark, without a knock, (they had their own key) to disturb my tranquillity. One was disorientated as she made her unsteady way towards the front door, the advance party having reconnoitred the way ahead and secured the lounge went back to find the missing detachment. There had obviously been some murmuring in the ranks on the way over from Wales but this was nothing unusual since the battalion had only recently been formed and discipline was weak.
The corporal in charge soon established control with a few homilies whilst blinking into the light came the main detachment heading, as always, for the toilet ! A little abashed at this early hour but soon finding her feet, looking for promotion and the sergeants stripes she quickly did the rounds.
The corporal meanwhile after establishing base and having fed the horses was not to be usurped and quickly did her own appraisal of the site for the nights bivouac. A place to obtain food (the fridge was full) a place to cook and wash and most important given the hour, a place to get their head down. My own part in this onslaught was of a rabbit caught in the headlights, impressed by the near military efficiency but startled by the near silence as the takeover was carried out.
King of my castle one moment I was soon reduced to that of a servant offering tea, sorry no milk (bad oversight) and a sandwich,( no thanks we carry our own provisions). Still there had been, until then no outright condemnation of the Quartermaster or the accommodation but this was early times and after the usual pleasantries a more detailed inspection of the barracks revealed a major problem, the sheet was not a sheet but a duvet cover and all hell broke out. How could one possibly make a mistake like that ? The opprobrium deepened with reference to ignorance and stupidity as a search broke out to find a sheet.
The flowers by the bedside were forgotten, the freshly washed towels laid neatly on the bed like a 5 star hotel were ignored for the missing sheets. For people so tired after such a long journey one could only wonder at such trivia but then any Achilles Heel in provisions  is useful to establish supremacy.
I can only quake at the thought of breakfast !!!