Recheck that everything is connected as it should (refer to the relevant manual(s) if you need to).
You said that you unplugged your computer, but did you remove the ethernet cable? It is possible that lightning struck the phone line to your house and the energy then travelled down the line, through the modem/router and then along the ethernet cable to your computer.
I remember experiencing many years ago (almost 40
) the effects of lightning striking a TV aerial. I had a TV in my bedroom, and it was one of those sets that employed valves (or tubes). It was unplugged, and I was lying on the floor doing a jigsaw puzzle. I was aware that it was raining heavily, and that there was thunder and lightning. All of a sudden, the screen of the TV lit up, and it was obvious that the aerial had received a direct strike. Fortunately, the set didn't appear to suffer any damage, and worked as normal afterwards.
The point I'm making here illustrates the enormous energy associated with lightning. The fact that the TV survived is probably down to the fact that it was a valve based set, which are far more resillient to those conditions than solid state ones.