How to prove that sender tempered with his own email content

Hi everyone, am new to a discussion forums, so be patient with me please. My acquaintance has emailed to me his bank details so that I could transfer money to his account. I have transfered the money as per the email, printed and scanned the bank transfer receipt, and used a reply button with attaching the bank transfer confirmation and wrote confirmation of my actions. The money has been debited from my account by my bank. However, later I have received another e-mail from my acquaintance, which looks like continuation of our e-mails, where he claimes, that I have missed a digit in the bank account number and that it is my fault. Surely enough, in the part of his e-mail where was the bank account one more digit was added now. I know, that he tempered with the content of his own email formerly sent to me. I would be plainly stupid attempting to credit someone's else account...
Please, how can I get an evidence to prove to him, that he changed/edited his own email content?
I don't want to use a reply button to his last email knowing that he edited the bank account number in lower parts of the email...
What are your thoughts guys? Regards Dale

You're being scammed. Try and get your money back. Either way I'd just ignore the guy.