Presumably the computer had a password set. This makes it non-trivial for an unsophisticated thief to unlock it, but there is a documented procedure to do so if

Presumably the computer had a password set. This makes it non-trivial for an unsophisticated thief to unlock it, but there is a documented procedure to do so if you know how to look it up: https://support.apple.com/en-us/102673 https://support.apple.com/en-us/102673