Did you sent this to an exchange? If so, in which exchange did you do this? They are the ONLY ones that may help you.
Contact their support. Some exchanges just help you, others charge a fee to recover your coins and others dont do anything. Just hope they help you, because no one else can.
If you own the wallet, recovering it could be possible (Im not sure tho, as we are talking about the ETH and BTC blockchain). Disclose some details (tx ids, wallets/services used, etc).
As I understand it, he has access to the wallet, but the wallet refuses to see the cache? Did I understand correctly?