I've had the drive fail right after turning the machine back on after a screen repair.
If he turns it back off improperly because he can't see the shut down button, that's on him.
If it fails for no reason after a properly performed repair, it's not on him.
I require customers watch what I do so they can't accuse me of any misconduct towards their machine. I understand both sides.
On one hand, the customer brings in a machine that didn't have that problem, yet it has it after a screen replacement. What did I do to their machine?
On the other hand, I've done 6-15 screen replacements a day for many years, and this problem has occurred twice to my memory. So that's a couple of thousand of repairs, and two have this problem. Yes, to me, it is utter coincidence when it occurs. I have made the mistake on my own personal machines of getting hasty with shutting them down when something is malfunctioning that limits my ability to see the screen, which caused the OS install to become corrupt. I'm impatient with my own things, like the mechanic that never has a working car or plumber whose toilet never flushes. However, the statistical probability of a drive randomly failing is close if not equal to the amount of machines that have had this problem/the amount of machines I've worked on.
There's no way to tell unless you saw exactly what he did. Most techs without the experience to not break something also lack the poker face to hide from you that they broke something! If he didn't remove the top case, there's little chance he destroyed the airport card. If he followed the iBreakit.com guide, then there's a chance he did, as these guides instruct you to remove portions of the machine unnecessary to get to the LCD. Is it no networks show up, or that the card is actually dead? He could have just pinched the airport antenna wires which ride up the LCD's frame on your machine.
My theory as to why Apple charges so much for these repairs is because they expect extra trouble. LCDs don't just break. They break because people are rough on their machines, so if the LCD has sustained shock or damage, typically, everything else has as well, and is now at a premature risk of failing. I keep that in mind when I work on the machines which is why I always encourage people to take a minimalistic approach to taking the machine apart to replace or repair something, as the entire machine has seen shock & damage to get to the point of requiring a repair.
I hope this sheds some light on your situation.