If he couldn't show the trace then no bank should've let him really: were I live, you have to show where fiat->crypto accused and how you got that fiat. Then you have to show how the crypto became worth more (that can just be a wallet address IN and wallet address OUT between the times it went from the fiat amount you started with until the time it became what you are trying to transfer to the bank). But that's all; few screenshots, even for large amounts. I guess if you are trying to send over more than a million, you might want to get some people to help you anyway. Also; always call your bank upfront to explain what will happen; that can prevent a freeze or reject if you got in ahead.