Definition of mysterious disappearance exclusion

policy clause that excludes coverage for loss of property if the cause of the loss cannot be identified. Mysterious disappearance is an exclusion in a standard inland marine insurance all-risks policy. Because some theft insurance policies do not contain this exclusion, they implicitly insure against mysterious disappearance and would cover the loss of a diamond necklace, for example, even if the owner did not recall how it had been lost.