In some cases, copies of POA's and wills get filed at local Clerk of Court's office, not sure about trusts. Ideally, when such a document is drawn up, all parties should have a certified copy & the attorney should keep one on file, as well as Clerk of Court. Then no matter what the comedy of errors, someone will have a valid copy that can be referred to. No one should have the "only copy" of anything, especially when survivors are part of the original arrangement & have a lot to gain or lose after one's death.
Remember the American heroes of Flight 93.