I still cant be sure if the damage came through the mains(my plug socket is still working fine) , or through the modem(Ethernet connection).
Your post implies you have forgotten how electricity works. A surge does not enter on one path, do damage, then stop. First that electricity in incoming on one path (ie AC electric). And simultaneously outgoing on some other path (ie modem). If that current is not incoming and outgoing simultaneously, then no surge exists.
So what was the incoming and outgoing path? Well, what exactly inside the laptop was damaged. What would have been the incoming and outgoing path through that part?
Notice the suggestion: outgoing via phone line. All phone lines already have a superior protector. That earthed protector is why surges often use the phone line as an outgoing (and destructive) path. Others, who forget how electricity works, then assume the surge entered on a phone line, did modem damage and stopped. Most have no idea that telcos 'install for free' a superior protector on every subscriber interface.
What can be a good path to earth? Incoming on AC mains. Outgoing to earth via the furniture. Why were wooden church steeples struck by lightning? Wood was an electrical conductor to earth. What can sometimes make appliance damage easier? An adjacent protector that also does not claim to protect from a typically destructive surge such as that Belkin. Even power off does not provide protection.
Stating exactly what was damaged is necessary to answer your question. Only computer techs who actually know how electricity works can provide that answer.
Meanwhile, earth lightning BEFORE it enters the building. Nothing inside (not even power off) can protect your appliances. Best protection is inside every appliance. Informed consumers earth one 'whole house' protector so that all appliances (dishwasher, air conditioner, clock radio, door bell, bathroom GFCI, etc) are protected. So that existing best protection is not overwhelmed.
First, did a surge do damage? Dead bodies are best evidence. Second, avert damage by earthing every incoming utility. But only you are responsible for installing, upgrading, and maintaining what would protect everything - single point earth ground.
