It is pertinent to have more than one backup of your wallet, if one of your flashdrives goes bad, you have another one to fall back to, you must also have your seed phrase on paper in addition to your flashdrive back up. Under no circumstance should your drive containing your Bitcoins ever get into the hands of a third party.
I believe he didn't know that the safest way to store Bitcoin was through the Hardware wallets because if he had chosen to store his holdings via a hardware wallet, there's no fucking way he would have been this unfortunate.
A person who can take their flashdrive containing a large amount of BTC to a data recovery person can obviously use a hardware wallet and still somehow lose their seed phrase stored on paper or mistakenly show it to someone else.
So the method used in storing someone’s holding doesn’t really matter much unless the person who is holding and making use of the wallet is careful enough.
One can still use the best wallet with the highest safety measure and still lose there money if they don’t take security seriously. Ignorant and what someone did not know is really a bad thing.