How would tamper evidence help if the device is stolen? If nobody but me has the device encryption key, and my device is stolen, I can be sure that nobody will

How would tamper evidence help if the device is stolen? If nobody but me has the device encryption key, and my device is stolen, I can be sure that nobody will have access to whatever data it contains. If anybody else has the device encryption key, however, and the device is stolen, I can no longer know whether anybody else had access to the data, no matter how much tamper evidence the device has.