Share some more info about it.
All he should share is the address. Anything else is unnecessary and will make verifying the true owner more difficult in the future. If he will not reveal the address, then the whole thing is pointless.
If it is encrypted this whole thread is completely useless.
Not at all. If it is encrypted, it stands to reason the true owner either knows or has access to the decryption key. If OP can reunite the encrypted key with the owner, then the owner can decrypt it and access their coins.