You repeat something so often that you come to know it as a fact, whereas it could of course turn out merely to be a myth.
My old professor Alvar Ellegård reputedly lost his PhD thesis (on the uses of the word do) down the ‘sopnedkast’ and had to re-write the whole thing.
I’m not sure whether us students were told this as an amusing fact, or if it was intended as a warning never to tidy our flats. And maybe he never did throw his thesis away. But it’s what I remember him by. That, and a textbook I actually hung on to for a surprisingly long time.
Sopnedkast is a rubbish chute. It’s what we had in the semi-olden days for getting rid of rubbish. And PhD theses, obviously. Keys were also pretty good to chuck down this hole-in-the-wall, as not infrequently you’d need the aforementioned keys both to re-enter your flat, or to gain access to the rubbish room with the bins, where the keys had ended up. (I never did this.)
What with recycling and sorting your rubbish properly, the chutes are long gone. Well, not gone gone; just firmly shut. People simply have to carry their well-separated items down all those stairs.
These days there is always the delete button. (For theses. Not so much for milk cartons and newspapers.)