Stolen in 1917, this 1,000-year-old manuscript was just returned to its rightful owners
https://edition.cnn.com/2022/10/01/world/christian-gospel-manuscript-return-greece-trnd/index.html
It's basically important to return stolen things totheir original places.
But, if they are stored in museum where temperature and humidity are kept at the most appropriate condition and original places do not own a device to adjust temperature and humidity, it may not be better to return to original planes in terms of maintaining historic things.
Those who involved in similar cases should think about the best way to maintain historically precious things.