Torah.org discusses a case where a guest in someone's house washed a cup and drank from it (without permission), and later discovered that there was a diamond there.
They answer that there is a Machlokes Rishonim between the Tosfos and Rosh on one side and the Ramban and Ran on the Other. According to the Tosfos, one is not liable where one damaged property if the damage was totally unexpected.
However, the Ramban says one is always liable.
Because people don't hide diamonds in coffee cups, according to Tosfos he would be patur, while according to the Ramban he would be Chayav.
The Mechaber rules like the Ramban, while the Rama quotes Tosfos. Therefore, if one didn't pay yet, the defendent could say "Kim Li" like the Rama and not only can Beis Din not force him to pay, but he is free in Diney Shamayim.