Of course that txn would show up on-chain, but if you don't have possession of the private key for the first account, and no digital device has ever "seen" the hardware account then he would've been fine.
This is assuming the key piece of evidence was his private key, and he wouldn't have been prosecuted without it.
Additionally, putting your key in cloud storage sounds like the dumbest thing ever... Just memorize your seed phrase and write it down. Its 4bn for christ sake.