Not really; he would have saved the private key into another HDD which could be thrown away mistakenly as this one. If I'm correct, having the wallet file stored is a quite good practice as people may have a few/hundreds/thousands of addresses used. In that case, the wallet file would have done the job though the master private key would also be the same. Regardless of whatever could have his bitcoin saved, it's his bad luck actually that he wasn't aware of the mistake.
Don't most people save the wallet file only?