NPR reports that during WWII, two Nobel laureates fleeing from the Nazis had to leave their prizes behind. They decided to hide them–but in plain sight. With the help of a chemist named Hevesy, the prizes were dissolved in an acid solution known as aqua regia. It worked well:
When the Nazis ransacked Bohr’s institute, they scoured the building for loot or evidence of wrongdoing but left the beaker of orange aqua regia untouched. Hevesy was forced to flee to Stockholm in 1943, but when he returned to his battered laboratory after V-E Day, he found the innocuous beaker undisturbed on a shelf.
Then, after the war:
[Hevesy] reversed the chemistry, precipitated out the gold and then, around January, 1950, sent the raw metal back to the Swedish Academy in Stockholm. The Nobel Foundation then recast the prizes using the original gold.