Exactly. Also, the OP refers to the Mona Lisa as an example. Ironically, the Mona Lisa gained global fame because of its theft from the Louvre in 1911 by Vinc

Exactly. Also, the OP refers to the Mona Lisa as an example. Ironically, the Mona Lisa gained global fame because of its theft from the Louvre in 1911 by Vincenzo Peruggia: the very man who had helped construct the panel's glass casing. As a patriot, Peruggia believed that the panel belonged to an Italian museum. After two years of hiding the painting in his apartment, he grew impatient. He got caught trying to sell it of to the director of the Uffizi in Florence. The Mona Lisa returned to Paris in 1914. Given the longevity of heritage institutions, theft or objects going missing is never a question of "if it will happen", but "when it will happen". Even with the best of systems in place, you can't rule out human error, or intentions. Finally, deaccessioning is a vital part of policies. Museums do auction off objects for various reasons e.g. because they are duplicative or not relevant or complementary anymore to the mission of the museum and its collection. ... and in some cases, they are forced to sell of objects in order to cover the bills. The Pandemic has added such pressures to many institutions, including the Met: https://www.nytimes.com/2021/03/19/arts/design/deaccession-museum-directors.html https://www.nytimes.com/2021/03/19/arts/design/deaccession-m...