that is if you believe this story
"An MI6 officer on her first mission to Colombia, the drug capital of the world, has lost a top-secret computer memory stick containing the names of key informers the Secret Intelligence Service has in South America, the Caribbean, North Africa, Spain and on across northern Europe into Britain, according to a report" source
with Data Leakage Prevention tools or techniques it would have been impossible to copy the information from the protected environment on the stupid usb
with encryption the data would have been without any use for anyone else than those that could trigger the decryption. Except some exceptional techniques in exceptional situations.