One of the many advantages of using a trust (rather than just a will) for your estate plan is that, if an original trust cannot be located, then (subject to a limited exception) a copy of the trust may be used in its place under the Evidence Code, which often allows for a copy of a document to be used in place of an original. The exception is for cases when there is other evidence to prove that the original trust is missing because the person who signed it intended to revoke it by destroying it.
In contrast, if an original will is in a person’s possession at the time of their death, and if they were not incompetent at that time, then the missing will is presumed to have been destroyed by that person with the intent to revoke it (California Probate Code § 6124). This rule is a throwback to the old English tradition of revoking a will by burning it in the fireplace. While the lost will rule is certainly rather antiquated, it still does cause problems for families from time to time.