If he has wallet.aes.json then he could try decrypting it with blockchain tool? (https://github.com/blockchain/my-wallet-backup-decryption-tool)
That's also another method, Op can try it if the above method didn't work
if you don't have the backup or unable to find it, try this thing below.
https://blockchain.info/wallet/ {Your ID } ?format=json
https://blockchain.info/wallet/ {Your ID } ?format=json
Haven't heard of this. @OP in case you have your .aes.json file/s, could you do this regardless? since this could be useful