Given the extraordinary wealth of material stored in Oxbridge college libraries, there is a wonderful inevitability that, from time to time, "lost" treasures will be uncovered.
Not all losses have innocent explanations: in the 19th century, The Queen's College, Oxford, mislaid a coveted statue of Queen Philippa, wife of Edward III, whose chaplain, Robert de Eglesfield, founded the college in 1341.
When it reappeared a short time later in a garden next to a local pub, it became apparent that the college had fallen victim to a student prank.
However, earlier this year a librarian at the same college recovered two remarkable treasures that had lain unknown among its manuscripts since at least the 18th century.
Veronika Vernier, its historic collections assistant, was sifting through more than 700 items in the manuscript cupboard, examining the old shelf marks and checking them against earlier catalogues.
Having attended a course on maps and map-making organised by the University of London's Rare Books School, her attention was caught by two 17th-century atlases.
Although they had been listed in 1816 and even had an earlier shelf mark, no further details were available. The titles seemed to be in Portuguese, a fact confirmed by a Brazilian butler in the senior common room, so Ms Vernier began investigating the cartographer, Joao Teixeira.
When her search led her to an antique map dealer offering a single copperplate sheet by the cartographer as a "scarce map that seldom appears for sale", it was clear that the Queen's manuscript atlases - containing 16 and 23 maps - were something special. She consulted Nick Millea, map librarian at the Bodleian Library, University of Oxford, who directed her to a six-volume "bible" of Portuguese cartography.
This listed only five other known copies of the first atlas, Description of the maritime ports of the Kingdom of Portugal, dating from 1648.
The other, unnamed, atlas turned out to be Plans of the cities and fortresses of the conquest of Oriental India, by the same cartographer in roughly the same year. Only four other copies were recorded.
Mr Millea said the atlases were "stunningly attractive" and "a very important find, because so few copies of this material exist and the ones at Queen's look almost new".
"It's great that they found them and that they were able to work out just how important they are," he added.
"You don't get discoveries like this every day or even every year: I don't remember anything of similar quality turning up at Oxford since I joined the Bodleian in 1992."
Many Oxbridge college libraries have major, sometimes world-class historic collections - Queen's alone has about 100,000 volumes published before 1850.
Such vast quantities of material are overseen by small teams of librarians who have many other demands on their time and inevitable gaps in their knowledge. They seldom convince their colleges that their needs are a priority.
As a result, extraordinary artefacts sometimes languish unnoticed, with no one able to appreciate their true significance or value.
Although delighted by the recent discoveries, Mr Millea said he suspected they would not be the last.
"There has to be a potential for similar things to turn up in college libraries," he said.