Shouldn't there be a police report filed here since a crime was committed? Obviously the airline doesn't have any interest in this matter, but the police might be interested. In the event that the stolen goods are found you would want a police report to support your claim that it is your stuff.
The airline said they don't accept laptops but in this case they did accept the laptop. I wonder what a lawyer would say about the situation. If they have a strict policy of not accepting laptops, they need to do a better job of enforcing the policy. Perhaps you could claim the enforcement of the policy was negligent???
Asking for a voucher as a reward because the employer's computer was stolen sounds like a weak argument to me.