INAL:
In my opinion, I would say the owner of the Laptop would have the right to grant you permission to retrieve any information you need, regardless of them using the Yahoo account, especially since the Yahoo account is being used to conduct business with the employer and with contractors of the employer.
Of course, the best bet would be to retrieve the laptop and then fire him. I understand that good help is hard to find over there, but they obviously don't have good help currently employed when it comes to this person.
If they hire a new person, make it very clear to them that all communications with the laptop can/will be monitored and the first instance of wrong-doing is immediate termination.





